About 160,000 refugees have fled along the main highway from Chechnya during Russia's month-long conflict with the separatist republic. But the road was taken by federal forces over the weekend, tightening their noose around the Chechen capital, Grozny.

Russia boosted its presence in Chechnya over the weekend, from some 60,000 troops to around 100,000, according to military sources.

Its forces yesterday fired missiles at what they described as "rebel military positions" around two Chechen towns. Chechen officials said 39 civilians had been killed in the attacks and dozens more were injured.

Residents reported further Russian attacks yesterday on the southern villages of Serzhen-Yurt and Vedeno; Bamut and Samashki, both in the west; and Goragorsky, in the north-west.

A total of 66 people were killed and more than 100 were injured, according to unconfirmed reports.

Alarmed by the closure of the only refugee corridor, the president of Ingushetia, Ruslan Aushev, said he would be appealing to the Russian prime minister, Vladimir Putin, to reopen the route.

"These people now have no way of getting out of Chechnya," he said. "They are mostly women, children and old people. The bandits are walking around as they please and the peaceful population are suffering most."

But Russia's intelligence service, the FSB, yesterday sought to justify the route's closure.

A spokesman insisted that the route had been used by rebels to smuggle fuel into Ingushetia, where it was being sold to help finance the Chechen guerrilla forces.

A network of rocky pathways south of Grozny, through the Caucasus mountains to Georgia, now represents the only exit route for fleeing Chechens and the only entry point for guerrilla reinforcements.

But the route is extremely treacherous. It is under frequent fire from Russian planes and becomes almost impassable once winter sets in.

Moscow denies that it was responsible for Thursday's brutal assault on Grozny's crowded market place. The US secretary of state, Madeleine Albright, was expected to raise the issue last night in a telephone conversation with the Russian foreign minister, Igor Ivanov. Russia insists that the conflict is an internal affair.

The prospect of a negotiated settlement to the crisis receded still further yesterday when the Chechens stipulated the terms on which they would agree to begin peace talks.

The Chechen vice president, Vakha Arsanov, said any negotiations must be conducted without Mr Putin, who is regarded as the initiator of the conflict. He said Russia must cease military action and withdraw its troops.