An early morning truck bomb blast killed 17 people in the southern Russian city of Volgodonsk, deepening a political and public crisis as the country's leaders struggled to respond to a string of three similar terrorist bombings in the past two weeks.

Today's explosion at 5:57 a.m. in Volgodonsk, 600 miles southeast of Moscow, tore the face off a nine-story, 144-unit apartment building. Local hospitals said 69 of the 115 wounded were hospitalized, 20 of them in grave condition. Police said the explosive charge, placed in a truck, had the force of about 650 to 1,100 pounds of TNT.

Russian officials have taken a harsh tone while ordering tighter security measures and searching thousands of buildings for explosives possibly planted by terrorists, who have sown fear across the country. Despite the nationwide dragnet, there have been no breakthroughs.

"We must strangle the vermin at the root," Prime Minister Vladimir Putin declared after reporting on today's explosion to President Boris Yeltsin. The bombings have once again stirred questions about Yeltsin's leadership, and there is speculation he may have to take more resolute action, although many politicians have urged him not to declare a national state of emergency or martial law.

Moscow Mayor Yuri Luzhkov, a potential presidential contender, accused state authorities of responding slowly to the attacks. Reeling off a list of terrorist incidents in recent years, Luzhkov said, "What measures did the state take? No measures were taken. . . . It was only after those terrible explosions in Moscow that our state authorities started realizing that some measures must be taken."

Nearly 300 people have been killed in four apartment bombings since Sept. 4, two of which occurred in Moscow. Putin and other Russian leaders have accused separatist rebels in the southern region of Chechnya of organizing the attacks.

Luzhkov called for retribution against the terrorists and left no doubt that he blames the Chechens, whom he called "a bandit community engaged in terrorism, slave trade and robbery."

Boris Berezovsky, the business tycoon close to Yeltsin's inner circle, also criticized the government, telling reporters today the Kremlin remained idle after the first blast. "It took another 118 lives to alert them," he said.

The string of bombings has unnerved Russians who, despite the political and economic turmoil in the country, have not faced such terrorism before. Some residential buildings organized search parties to check out long-forgotten storerooms for bombs, while others stationed their own guards outside.

Dark-skinned people from the Caucusus region of southern Russia have faced constant questioning and police checks. One Moscow resident ordered new kitchen furniture this week only to find the delivery men in a quiet panic. One of the recent bombs went off in a furniture storeroom, and the dark-skinned delivery men feared that neighbors would besiege their truck.

In response to the bombings, there have been growing demands for punitive action against Chechnya, such as creating a demilitarized zone around its border. Russia's air force chief, Col. Gen. Anatoly Kornukov, said planes raided Chechen guerrilla bases today, adding that "we can no longer permit what has been happening."

But others have warned that Russia's neglect of Chechnya in recent years is one reason for the latest violence. Russian troops were defeated militarily in their two-year war with the separatist region, but a final decision on Chechnya's political status was put off for five years in a 1996 cease-fire agreement.

Since then, critics say Russia has ignored Chechnya's deepening economic and social problems as well as the fact that Chechen President Aslan Maskhadov appears to have lost control of the territory.

Recently, a group of Chechen guerrillas seeking to establish an Islamic state in the neighboring region of Dagestan have been battling Russian troops. Russia also laid siege, separately, to a pair of villages controlled by Islamic militants inside Dagestan.

Berezovsky, who has long had close ties to Chechyna, predicted today that the terrorism would continue. "Moscow has not fulfilled a single economic program, leaving these armed and hungry people without work and hope in the future," Berezovsky said of Chechnya, adding that "bomb attacks in Russia will continue for a long time, and the country has no strength or money to stop them."

In Volgodonsk, bloodied residents of the apartment building were rushed to local hospitals in a scene repeated over and over in recent days as chunks of prefabricated concrete blocks were scattered about like children's toys.

Residents recalled seeing a truck parked at the spot of the explosion, but authorities said it was possible the explosives were hidden in a sewer main; the blast left a large crater.

Earlier, a prominent journalist with experience in Chechnya had said he had learned of plans to bomb 10 Russian buildings to retaliate for Russian attacks on the Chechens. The Federal Security Service said today it uncovered a set of timers scheduled to go off in the days ahead, while Moscow police said they had found 76 sacks of explosives weighing about 3.5 tons nestled among sacks of sugar that had been brought into the city.

In St. Petersburg, meanwhile, an explosive device went off in an apartment building at the door of an unidentified family, killing two people and injuring four. Authorities said, however, that the blast did not seem to be linked to the four terrorist attacks.

One officer said it appeared to have been caused by about six to nine pounds of TNT, "but I would not describe it as a terrorist act, at least nothing like the Moscow blasts."

He added that the explosion was more likely "an attack on the residents of the apartment."

Two Weeks of Terror

Yesterday's bomb blast outside an apartment building in the city of Volgodonsk was the fourth such explosion in Russia in two weeks. More than 270 people have died in the attacks that some officials have attributed to Chechen separatists. More blasts may have been prevented when a cache of explosives was discovered outside Moscow yesterday.

Sept. 9

Bomb blast in apartment building.

94 killed; 150 hurt

Sept. 13

Bomb blast in apartment building.

118 killed; 5 hurt

Sept. 16

Truck bomb blast at apartment building.

17 killed; 115 hurt

Sept. 4

Car bomb blast at military housing complex.

64 killed; 100 hurt