Russian President Vladimir Putin has ordered an investigation into the crash of a helicopter that claimed at least 74 lives in break-away Chechnya. Chechen separatist rebels are claiming to have downed the helicopter loaded with Russian soldiers.
The aircraft was carrying 127 soldiers and five crew when it went down.
Russia's Deputy Prosecutor General says a criminal case is being opened into the accident.
Chechen separatist websites quote guerrilla sources as saying they brought down the aircraft with a surface-to-air missile.
If the Chechen claim is true, it would be one of the biggest losses of federal troops in a single battle incident in the long-running guerrilla war.
Russian sources commenting in the first hours after the disaster made no mention of the Chechen claim. A spokesman for the Russian Defense Ministry said only that a fire in one of the aircraft's engines forced the craft to make an emergency landing.
Fire continued to burn hours after the crash, hampering efforts to determine the full number of casualties.
Russian television quotes witnesses as saying the helicopter went down in a minefield.
A Deputy Commander in the North Caucasus said that according to the latest information he has received, more than 30 injured people have been taken to the hospital. But he stressed that most of the wounded had been treated at the crash site. He says the priority now is to organize rescue work.
Chechen separatists have recently stepped up actions against Russian federal forces in the break-away republic, including attacks late last week that killed nine servicemen and five civilians.
Russian Defense Minister Sergei Ivanov expressed his condolences to the families and relatives of the dead and injured soldiers. President Putin called it a catastrophe.