Chechen rebels using a shoulder-fired missile shot down a Russian military helicopter Thursday in the mountains, killing three of the crew, the military said. 

The attack in Chechnya was the latest demonstration of the separatists' capacity to kill Russian forces despite being outnumbered and outgunned.

At least seven other Russian servicemen died in attacks and rebel land mine explosions over the past day, an official in the Moscow-backed Chechnya administration said on condition of anonymity.

The missile attack occurred after the Mi-8 helicopter delivered paratroopers to an area just north of Vedeno, said a duty officer for the military's North Caucasus command in Rostov-on-Don. He said the helicopter was downed with an Igla missile, which is fired from a shoulder launcher.

Vedeno is in the heavily wooded mountains that make up the southern third of Chechnya and provide shelter for the rebels. Many insurgents are believed to be based in the mountains. Rebel infiltration into Grozny, the Chechen capital, is substantial despite a huge Russian military presence.

Also Thursday, Russia artillery shelled suspected rebel positions in the Urus-Martan, Vedeno, Shali and Nozhai-Yurt districts and federal forces detained at least 150 people in a series of sweeps throughout the republic, the Chechen official said.

The reports followed the pattern of bloody stalemate that has characterized most of the nearly four-year Chechnya war. The rebels inflict daily small attacks on Russian forces, who respond with air and heavy weapons barrages, but neither side appears to have made significant or permanent gains over the past year.

Russian forces withdrew from Chechnya in 1996 after a 20-month war with separatists, after which Chechnya gained de facto independence and was plagued by lawlessness. Russian forces swept in again in September 1999 after Chechnya-based insurgents mounted incursions into neighboring Dagestan and after some 300 people died in explosions that authorities blamed on the rebels.

The Kremlin has been eager to show the situation in Chechnya as normalizing, lauding a March referendum and October presidential elections as concrete steps to peace.