Russian military advances into rebel-held southern Chechnya have trapped civilians in cellars and sent others fleeing through snowy mountain passes and forests littered with corpses, Chechen officials said today.

After days of heavy fighting, the Russian military claimed to have made inroads into Chechnya's southern mountains, capturing strategic heights overlooking Vedeno, a major rebel stronghold. Russian forces can now position artillery on the heights, making it easier to drive the rebels out.

But the constant air and artillery attacks that preceded the advance of Russian troops have left civilians trapped in southern mountain villages, afraid to venture out with bombs and shells raining on the roads, Chechen officials and civilians said.

Residents of Grozny, the Chechen capital, who had fled the city in hopes of escaping to neighboring Georgia have been stuck in the villages of Itum-Kale, 50 miles south of Grozny, and Shatoi, 35 miles south of Grozny.

"People cannot venture out of their homes because the shelling continues around the clock," said Ramzan Bisiyev, head of the village administration in Rodina, just outside Grozny. Bisiyev has been trying to negotiate with Russian authorities for a safe corridor so civilians can leave southern Chechnya for Russian-controlled areas in the north.

Having swept across the plains of northern Chechnya, Russian forces have been trying to crush separatist rebels concentrated in the mountainous south. After taking the heights near Vedeno, Russian troops seized a large cache of arms and ammunition, including grenade launchers, two antiaircraft rocket launchers and several flamethrowers, said Maj. Alexander Diordiev, a military spokesman.

Russian forces also kept up air and artillery bombardments of Grozny--the only rebel-controlled city in northern Chechnya--as a major offensive to take it entered a second week. Russian commanders said their forces fought off a rebel attack on artillery positions northwest of Grozny, on the Tersky Heights.

Russian commanders said their ground forces are making progress in Grozny, but troops still appear to be far from taking the capital from rebel defenders in heavily fortified positions.