A Russian transport helicopter jammed with troops crashed in Chechnya on Monday, and Russian news agencies said as many as 85 servicemen were killed. Russian officials said they did not know how many were killed or if the aircraft was shot down by rebels.

Reporting an engine on fire, the pilot wanted to make an emergency landing near Russia's front-line base for its battle with separatist rebels, one Russian official said.

The Mi-26, described as the world's largest helicopter, was carrying at least 132 people as it crashed and burned near the Russian military headquarters at Khankala outside Chechnya's capital of Grozny, said Col. Boris Podoprigora, the deputy commander of Russian troops in Chechnya.

Podoprigora said 32 survivors were hospitalized and doctors were treating other wounded people at the scene. Officials said the wreck burned for at least an hour after the crash.

He did not give a death toll.

Later, the Interfax news agency, citing an unidentified source at the military headquarters, reported that 142 people were on board the helicopter.

Sergei Fridinsky, a deputy prosecutor general, told Interfax dozens were dead and wounded, while Russian Defense Minister Sergei Ivanov offered his condolences to relatives of the servicemen killed. His statement, issued through the Defense Ministry, did not provide a death toll.

Earlier, Interfax reported that about 80 servicemen were killed, citing a source at military headquarters. ITAR-Tass, also citing a source there, put the death toll at 85.

Fridinsky said investigators were examining two possible causes of the crash: the helicopter was shot down by rebels or it suffered a technical problem.

A high-ranking source at the military headquarters said authorities believed it was more likely a technical problem, but nothing was being ruled out.

The head of the Defense Ministry press office, Nikolai Deryabin, told ORT state television the pilot requested permission to make an emergency landing because an engine was on fire.

Fridinsky said the helicopter fell onto a minefield. Podoprigora could not confirm that, but he said rescuers were working in difficult conditions at the site, which Russian television networks said was cordoned off.

Podoprigora said the Mi-26 is designed to carry 82 people. Officials did not say why there were 127 servicemen aboard the flight from a military base at Mozdok in neighboring Ingushetia. Authorities said all five crew members survived.

President Vladimir Putin ordered a thorough investigation into the crash, which ITAR-Tass said was the worst in Russian army history.

The crash came amid a spate of rebel actions against Russian forces in Chechnya, including attacks last week in the southwest that killed nine servicemen and five civilians.

Some analysts surmised that rebels intensified their actions to underscore the need for the Russian government to enter peace negotiations. A Chechen rebel representative met with a former head of Russia's Security Council in Geneva last week to discuss restarting talks stalled since last year.

Russia's government maintains that the war it launched in the breakaway Caucasus Mountain republic in fall 1999 is all but over, with just isolated groups of rebels holding out. However, Russian soldiers are killed almost every day by rebel attacks that sap military manpower and morale.

In September 2001, two generals and 11 other Russian servicemen died when their helicopter was shot down by a shoulder-fired missile shortly after takeoff from Grozny.

Another helicopter, an Mi-8 carrying two top Interior Ministry officials and 12 other people, crashed in Chechnya in January. The Kremlin said that crash was an accident, but an official with the Moscow-appointed civilian administration for Chechnya said investigators found fragments of the helicopter suggesting it also was shot down with a missile.

Military helicopter crashes are fairly common in Russia, where aging craft are often used to ferry soldiers or civilians to remote areas hard to reach by road, rail or plane.

Russian forces withdrew from Chechnya following a devastating 1994-1996 war that left separatists in charge, but they returned in 1999 after Chechnya-based militants invaded a neighboring region and the Kremlin blamed rebels for apartment-building bombings that killed 300 people in Moscow and other cities.