Russia has opened a new offensive against Islamic separatist forces in the southern republic of Dagestan, and officials said today that eight Russian soldiers have died in the three days of fighting.

The new warfare came just days after Prime Minister Vladimir Putin declared victory over a group of Islamic fighters who had crossed into Dagestan on Aug. 7 from the neighboring region of Chechnya and seized several villages near the border. The rebels' declared aim was to expel Russia from Dagestan, but after heavy attacks, they appeared either to have been forced back into Chechnya or wiped out.

"The Chechen gunmen had made an extremely bad mistake," Putin said in a newspaper interview published today.

Fighting resumed Sunday, however, and since then Russian Interior Ministry forces have taken control of two Islamic villages just southwest of the capital, Makhachkala, that had been a center of Islamic rebellion in recent months. Spiritual leaders there had declared their independence from Dagestan last year and instituted Islamic law. At the time, Russia did little about it.

But just after the fighting ebbed along the border, Russian officials apparently decided to attack the Islamic villages near the capital. Russian news reports today suggested that the operation did not go well. The guerrillas encamped in the villages--estimated to number several hundred--were well armed and reportedly had air defenses.

Moreover, Russian soldiers made "serious mistakes" in preparing the offensive, according to one television report, and failed to capture the high ground or use the element of surprise. The Russians were met with heavy resistance, according to the Interfax news agency.

Russian troops also were hampered by heavy rain and fog in the region, which although mountainous is closer to the Caspian Sea than the site of the earlier conflict.

Monday and today, Russian helicopter gunships made eight rocket attacks on the outskirts of the villages, and Grad multiple-rocket launchers were brought into action. Russian planes also dropped bombs near the villages today, targeting guerrillas who had dispersed in the hills.

In Moscow, President Boris Yeltsin vowed on Monday "that we will oust all the bandits from Dagestan. Dagestan will be cleared. Dagestan will be free."