President Boris Yeltsin today blamed "military sloppiness" for the setbacks of Russian forces in Dagestan, as the sudden thrust of Islamic rebels from Chechnya into the southern Russian region unleashed a tide of recriminations here.

Despite Russian air and artillery bombardment, a phalanx of about 2,000 guerrillas had advanced by nightfall to within three miles of Khasavyurt, a major Dagestani town. Their announced goal is to capture Khasavyurt and turn it into the Islamic capital of Dagestan. Meanwhile, the rebels remained in control of another large town, Novolakskoye, and six villages just inside the Dagestani border.

The heavily armed Chechens crossed into Dagestan on Sunday--the guerrillas' second such foray since early August--taking Russian troops and Interior Ministry paramilitary forces there by surprise. The Chechens are led by Shamil Basayev, a seasoned guerrilla commander who gained widespread notoriety during Chechnya's stalemated war for independence from Moscow several years ago. He has vowed to expel Russian forces from the region.

The guerrillas entered Dagestan "like a knife into butter," said Gennady Seleznov, speaker of the lower house of the Russian parliament, the State Duma. At least 24 Russian soldiers have been killed since the latest fighting began, compared with 49 in the previous month. The death toll among the guerrillas has not been reported.

"How did it happen we lost a whole village? The whole district, to be precise!" Yeltsin exclaimed to reporters before meeting today with Prime Minister Vladimir Putin. "How did it happen?" He noted that a car bomb blast that killed 64 people in an apartment complex housing Russian officers and their families Saturday night occurred in a closed military compound. "This is sloppiness of the military," he said.

Yeltsin convened the Kremlin security council, which he personally chaired to underscore the gravity of the situation. Yegor Stroyev, the speaker of the upper house of parliament said later that the council decided to cast the conflict as a fight against terrorism rather than an ethnic civil war.

At the outset of the session, Yeltsin read a statement to reporters that said: "These bandits are wrongly called Islamists. They fight against the Muslim peoples in Dagestan. . . . Terrorists have no nationality or faith. They have no God or Allah. They are degenerates and murderers."

The security council also decided to set up a military "information center" and to appeal to other nations to cut off the flow of arms to the guerrillas, Stroyev said, but any military decisions made were not disclosed. Yeltsin called for responding "quickly and decisively," but he stopped short of firing any officials, as he has sometimes done in times of crisis.

The fighting has already unsettled Dagestan, a poor, multi-ethnic region on the west coast of the Caspian Sea that is being convulsed by streams of refugees and by self-styled "home guards"--essentially vigilantes who are arming themselves to fight the rebels. While Yeltsin was criticizing his generals, politicians and analysts here pointed to larger factors contributing to the crisis, including Yeltsin's inattention to long-festering problems in the Northern Caucasus, especially in Chechnya. Many said the conflict underscores once again the weakness of Kremlin rule over Russia's diverse and widespread regions, and some blamed an ill-fated Interior Ministry decision last week to launch an attack on two Muslim villages in Dagestan whose inhabitants follow a conservative form of Islam.

Emil Pain, director of the Center for Ethnopolitical Regional Studies who once served as an adviser to Yeltsin on Chechnya, said the guerrilla incursion took advantage of political weakness in Moscow. "The federal center is weak," he said. "The president has a lot of powers under the constitution, but having a sick president, a president who is not supported by regional leaders and by the majority of parties, complicates the problem of control in general. . . . Everybody understands that this center is so immobile that it won't be able to retaliate."

For months, there was speculation in Moscow that Yeltsin would meet directly with Chechen President Aslan Maskhadov, but the meeting never took place. Pain called this a lost opportunity, since it now appears that Maskhadov is losing control over the separatist region. "The only way for Russia to [have prevented] this conflict was to make a deal with Maskhadov; only together could they put up resistance to Basayev."

Pain said the decision by Interior Ministry forces last week to besiege Karamakhi and Chabanmakhi--the two conservative Muslim villages--was a major mistake. Islamic leaders there had declared they no longer recognize the secular government of Dagestan, but those leaders had been tolerated by civil authorities for some time.

After putting down the first cross-border incursion in the Botlikh region of Dagestan several weeks ago, Interior Ministry forces turned their fire on the two villages, which are situated near Makhachkala, the Dagestani capital. Soon after that attack, the car bomb blast destroyed the nearby Russian officers' quarters.

"Starting a war in the center of Dagestan . . . almost within sight of Makhachkala, was a gross error," said Alexei Malashenko, a scholar in residence at the Carnegie Endowment for International Peace here. "I don't see any deep intrigue here; I see elementary incompetence."

Seleznov, the Duma speaker and a Communist, called Yeltsin's criticism of the army "totally unfair." "People in epaulets have nothing to do with it," he said. "We do not see the political will of the president; we see no political will of the government to take decisive measures in advance, and not after the fire starts."

When Interior Ministry units quickly became mired in the spreading conflict, Russian authorities committed regular army troops. Those troops were still engaged in fierce battles today, and Russian news agencies reported that army special forces units were entering Karamakhi.

Roman Popkovich, chairman of the Duma defense committee, said the attack on the two Muslim villages was "absolutely inexpert. It was done without the coordination and support of Defense Ministry troops."

CAPTION: Women weep for relatives slain in a strike by Russian aircraft Monday on the Chechen village of Zamai-Yurt, near the Dagestan border.

CAPTION: Chechen commander Shamil Basayev leads about 2,000 guerrillas in Dagestan, where he has vowed to expel Russian forces and establish an Islamic state.