Russian helicopter gunships Saturday attacked gunmen surrounding villages in the Caucasus region, near the border of breakaway Chechnya, officials said.
The Russian Interior Ministry said it launched an aerial assault to quell the violence in Dagestan, a southern Russian republic.
Fierce fighting was reported in the area, the heart of Russia's most troubled and violent region. Civilians streamed out of the area, the ITAR-Tass news agency said.
The gunmen appeared to be from the fundamentalist Wahhabi Islamic movement, also blamed for an attack last week in the nearby Tsumadi district, Dagestani authorities said. The group has been active in Chechnya and Dagestan since the 1994 launch of Chechnya's war for independence.
Dagestan has long been restive, and gun battles and bombings in recent days have given rise to fears that Chechen gangs, backed by Dagestan's extremist groups, were planning to take over the republic.
The militants crossed from Chechnya into Dagestan early Saturday and took up positions around the villages of Ansalta and Rakhata, Interior Ministry officials said.
No casualties were reported.
Dagestani authorities put the region under a "general alert," and ordered all vacationing military officers to return to duty.
Federal authorities dispatched 1,000 police, an Interior Ministry battalion and a motorized rifle brigade to the region, Interfax said.
Authorities initially estimated the number of gunmen at between 200 and 240. Late Saturday, ITAR-Tass reported an Interior Ministry estimate that there were at least 2,000 gunmen in the area.
Prime Minister Sergei Stepashin, the former interior minister who played a key role in Russia's botched war in Chechnya, said Moscow "will not repeat its mistakes of 1994-95 in the northern Caucasus," Interfax said.