Violence has spilled over from Russia's conflict in Chechnya
At least 20 insurgents have been killed in an operation by Russian security forces in the restive republic of Ingushetia, officials say.
Fighting erupted after troops surrounded a group of militants in a mountain forest near Chechnya's border.
Russia's interior and defence ministries and the Federal Security Service launched the sweep on Thursday.
Fighting by Muslim militants against Russian rule has stepped up in the past two years in Ingushetia and Dagestan.
Russian troops had sealed off a five sq-km-area blocking in the militants on Thursday, and the operation was said to be continuing.
"It was launched on a confirmed tip. A large base of [warlord Doku] Umarov's men was spotted near the village of Arshty," said an FSB official said.
Russian forces have fought two wars against separatists in the mainly Muslim republic of Chechnya since 1994. The conflicts claimed more than 100,000 lives and left the region in ruins.
Although Chechnya has been more peaceful in recent years, sporadic violence continues, and President Dmitry Medvedev says violence in the North Caucasus remains Russia's biggest domestic problem.
He says ending the acute poverty in the region is vital for restoring stability.
Experts say many young men in the region have joined a hard core of Muslim militants to fight for independence as a result of poverty and widespread abuses by the security forces, including kidnappings and torture.