MOSCOW, OCT. 4 (MONDAY) -- Military units loyal to President Boris Yeltsin launched an attack on the rebel parliament early today, after thousands of armed anti-government demonstrators routed police, seized key buildings in the capital and fought a pitched battle with guards at the state television complex.

Shortly after dawn, the area around the massive parliament building, known as the White House, shook and thudded like a city at war as dozens of armored personnel carriers and tanks manned by troops loyal to Yeltsin engaged in fierce firefights with supporters of the rebellious parliament.

As plumes of smoke from burning buildings and vehicles rose into the chill autumn sky, paratroops from the elite Taman and Dzerzhinsky divisions were reported to be moving in behind the armored vehicles, preparing to storm the building and a neighboring skyscraper occupied by the hard-line rebels Sunday. The skyscraper appeared to be on fire.

The attack was launched after last-ditch negotiations between Yeltsin aides and his opponents broke down following a Sunday of violence in Moscow that was unprecedented since the civil war seven decades ago.

"Today, the fate of Russia and the fate of our children is being decided," Yeltsin said in a televised statement read by an announcer Sunday. "The forces of civil war will not succeed."

Sunday's clashes between demonstrators and police left at least 20 people dead and scores wounded. Thousands of people joined anti-government attacks and demonstrations Sunday, and thousands of others gathered near the Kremlin in support of Yeltsin after his top aides appealed on television for help.

Dozens of armored personnel carriers and tanks moved into the center of Moscow, and about 40 were reported to have gathered at the Defense Ministry and the Kremlin. Highly placed defense sources reported that Russian Defense Minister Pavel Grachev and his top generals met for several hours as the violence erupted and agreed to throw their support to Yeltsin. Military districts across the country were contacted and appeared to be staying in the Yeltsin camp, the sources said.

By early this morning, anti-government forces were once again concentrated at the parliament headquarters and continued to hold the mayor's command center, while police had regained control over some other installations, including the Russian Tass news agency. Fighting raged on at the television center, where the most serious clash occurred Sunday after anti-government forces tried to storm the facility. Government officials said tanks and armored personnel carriers bearing pro-Yeltsin forces had been dispatched to the scene.

Other Russian cities appeared calm, and there were no reports of clashes outside Moscow. Indeed, much of Moscow outside the battle zones appeared normal, and most people knew nothing of the day's events unless they tried to drive through town or watched television. Aides said Yeltsin was spending the night in his Kremlin office.

Moscow, which had been gripped by a 13-day standoff between Yeltsin and the conservative Russian parliament, was convulsed Sunday by nightmarish scenes of civil war, punctuated by explosions and gunshots.

Jeering anti-Yeltsin demonstrators surrounded government buildings and taunted, "Rats, come out! Rats, come out!" Men in Cossack hats careened through the city in stolen police trucks, while young boys carried police shields and concertina wire away from the scenes of battle.

{In Sacramento, Calif., on Sunday, President Clinton blamed the parliamentary faction for the violence and restated his virtually unconditional support for Yeltsin, who he said had "bent over backwards" to find a peaceful resolution to the crisis.

{"We cannot afford to be in the position of wavering at this moment or backing off or giving any encouragement to people who clearly want to derail the election process and are not committed to reform in Russia," Clinton said.}

The violence in the capital began Sunday afternoon, when about 7,000 hard-line communists and militant nationalists -- supporters of the parliament, which Yeltsin ordered dissolved on Sept. 21 -- marched through the city. Police put up little resistance, and the demonstrators swarmed into the parliament building and the Moscow mayor's command center next door, seizing hundreds of weapons and vehicles abandoned by fleeing police.

American diplomats and their families living in the nearby U.S. Embassy compound were evacuated Sunday night. U.S. officials reported that all Americans were believed safe, although they continued to worry that the demonstrators, many of them hostile to the United States, might come over the embassy's high brick walls.

At the urging of Vice President Alexander Rutskoi -- Yeltsin's chief rival and the man whom the parliament proclaimed president -- the demonstrators moved on to occupy the first floor of the Russian Tass news agency and attack the television transmitting center. Both national networks went off the air suddenly around 7:15 p.m. as a newscaster near tears was describing the building's encirclement, but Russian television later began fitful pro-Yeltsin broadcasts from a secret location.

Yeltsin flew by helicopter from his country house to the Kremlin and declared a state of emergency in Moscow. In a statement read on television moments before it was cut off, the government said it would use "force to terminate the actions of political adventurists." CNN showed Yeltsin walking extremely slowly through the Kremlin courtyard upon his return, but he did not appear on Russian television.

Yeltsin's opponents, who jubilantly festooned the parliament and the captured mayor's office with red Soviet flags, declared themselves in control of the government and said Yeltsin and his advisers would be held accountable for a "coup d'etat." They promised a new "revolution" was beginning in Russia. The flags, pro-Soviet Union rhetoric and red Communist Party banners appeared to indicate that some were hoping for a Bolshevik-style takeover, but others said they were only defending democracy against Yeltsin, whom they described as a dictator.

Yegor Gaidar, first deputy prime minister of the Yeltsin government, made a televised appeal Sunday night for all Yeltsin supporters to gather in front of Moscow's City Hall to "defend our future and the future of our children and to prevent our country from once again being turned into a concentration camp."

By 1 a.m. today, 50,000 had gathered, including many young people and veterans of the Afghan war, and more streamed toward the Kremlin. As far as could be seen, they were unarmed but were forming into "brigades" and were constructing barricades around City Hall.

The Kremlin itself appeared quiet, with no sign of imminent attacks.

"Order will be restored in Moscow in the shortest time possible," Yeltsin's statement said. "We have the forces necessary for this."

In preparation for a possible army attack, the hard-liners inside the parliament indicated they were mining the area. Early Sunday evening, Rutskoi warned the armed forces that they had "only seconds" to rally to his side. At least some policemen appeared to have heeded his call and joined the forces at the parliament building. Some units marched toward the parliament building Sunday afternoon but appeared to be doing so under duress.

Yeltsin issued an order Sunday night naming Prime Minister Viktor Chernomyrdin as his successor in the event of his "incapacitation."

Yeltsin and his opponents have been locked in political battle for much of the last year. The Russian leader has pushed vigorously ahead with radical economic reforms, but his opponents -- hard-line communists, ultranationalists and centrists opposed to the speed of the reforms -- have accused him of ruining Russia and allying it too closely with the United States and the West.

Yeltsin brought the crisis to a head on Sept. 21 when he ordered parliament disbanded and set elections for a new, bicameral legislature on Dec. 12. Lawmakers, in response, blockaded themselves in the parliament building, impeached Yeltsin and replaced him with Rutskoi. Yeltsin then surrounded the parliament with thousands of Interior Ministry troops, barbed wire and water cannons and refused to let anyone pass.

But Yeltsin had pledged not to storm the parliament or use force to end the crisis. In fact, talks between his chief of staff and parliamentary officials were continuing at the residence of Russian Orthodox Patriarch Alexei II on Sunday even as the street clashes began.

Sunday's events began with a rally of about 7,000 parliament supporters beneath a giant statue of Lenin in October Square. Lines of police, clearly unprepared for the size of the crowd, used tear gas in a failed attempt to keep the demonstrators in the square.

The demonstrators marched along Moscow's inner ring road toward parliament, their numbers growing as they marched, and overran police lines several more times. At the White House, as the parliament building is known, Interior Ministry troops fired into the air but failed to stop the advance and quickly fell back in confusion.

Hundreds of shots were fired at one point, though in the chaos it was unclear who was shooting. Two policemen were killed.

Rutskoi emerged from the parliament building onto a balcony and urged his cheering supporters forward. The demonstrators, almost without a fight, occupied a skyscraper next door that belongs to the Moscow mayoralty and captured Deputy Mayor Alexander Braginsky. He was later released in exchange for a group of City Hall deputies who had been arrested earlier.

About 200 demonstrators then surged to Russia's Defense Ministry, where the nation's nuclear controls are located and its top generals were meeting. The ministry locked its doors and kept the crowd out without incident.

But thousands more, commandeering the water-cannon and troop-transport trucks that police had used to cordon off the parliament, headed toward the main television transmitter and other facilities crucial to controlling the nation's media. Most of the media, especially state television, have unabashedly supported Yeltsin since his Sept. 21 decree.

By 7 p.m., at least 2,000 demonstrators had surrounded the two main buildings of the Ostankino television center -- about eight miles from the parliament building -- which appeared to be guarded by only about 60 frightened police officers. A huge roar went up from the crowd as a captured military truck rammed the glass doors of one building. The demonstrators rushed into the building and took up gun positions on the second floor.

Within minutes, however, two huge explosions sounded, the ground floor erupted in flame, and tracer bullets flew from a second television building. Then fire from grenade-launchers shattered the rebels' position, and at least 20 people caught between the two buildings fell. Several appeared to have been killed and a dozen wounded, including demonstrators and journalists. A fierce gun battle between the two buildings kept rescue teams away from the wounded for at least 20 minutes.