MOSCOW - A Russian military helicopter, designed for 80 people but carrying at least 132, crash-landed in a minefield near the main military base in Chechnya yesterday, causing explosions that increased a death toll believed to be in the dozens, officials and news agencies reported.
A number of soldiers apparently survived the crash only to activate mines on emerging from the wreckage.
It appeared to be the worst air disaster since Russia began its second war in Chechnya nearly three years ago.
Initial reports indicated that the helicopter - an Mi-26 transport craft known as "the cow" because of its size - had been shot down by Chechen rebels. But amid the rescue effort, officials said the copter's pilot, Maj. Oleg Batanov, had reported a fire in the right engines moments before crash-landing short of the base's airfield.
Some reports put the death toll as high as 100, but Russian military officials had not released an official count by early this morning. They reported that at least 32 soldiers and crew members had survived and were being treated at a military hospital on the base, in Khankala just east of the Chechen capital, Grozny.
The rescue effort was delayed until explosives experts could clear a path for emergency workers through the mines, which encircle the Russian base, according to news reports.
Mines first went off when the helicopter came down, setting it ablaze. Soldiers clambering out of the aircraft set off more of them; the site was strewn with bodies, according to an online report by the newspaper Kommersant early today.
In its scale, the crash was comparable to the sinking of the nuclear-powered submarine Kursk in the Barents Sea, which killed all 118 crew members just over two years ago. President Vladimir V. Putin, whose response to the Kursk disaster was criticized as cold and uncaring, immediately called for a commission to investigate the cause of the crash.
"This catastrophe must be investigated most thoroughly," he said unemotionally during a televised meeting with his Cabinet ministers hours after the crash.
Whatever its cause, the incident was perhaps the single deadliest in Russia's drawn-out campaign to crush Chechnya's separatist movement. It was another heavy blow to the morale of the Russian military, which is struggling to contain a war of attrition with Chechen fighters.
It occurred during some of the most intense fighting in Chechnya this year. In recent weeks a series of clashes has belied Russia's claims of military dominance over the Chechens. Fierce fighting was reported over the weekend around Urus-Martan, 25 miles southwest of Grozny, with rebel ambushes killing at least 12 Russian soldiers or police officers.
The defense minister, Sergei Ivanov, expressed condolences to the families of the soldiers killed and pledged to help them. "The servicemen of the armed forces are in grief over the premature loss of their comrades in arms," he said in a statement released by the official news agency ITAR-Tass.
The helicopter crashed just before 5 p.m. yesterday about 1,000 feet short of the Khankala base. It had been ferrying soldiers to Khankala from the main Russian staging base at Mozdok, in the republic of North Ossetia.
The Mi-26 helicopter, which first entered service in 1983, is one of the largest ever built. It is designed to carry a standard load of about 80 passengers.
Boris Podoprigora, deputy commander of Russian forces in the Northern Caucasus, said 127 passengers, as well as five crew members, were on board, indicating the helicopter was severely overloaded.