Russia is to send air crash experts to the former Soviet state of Kyrgyzstan to help examine the flight data recorders for clues as to why a Tehran-bound Boeing 737-200 crashed late on Sunday.
Kyrgyzstan announced a national day of mourning for Tuesday after 65 people died in one of the Central Asian state's worst air disasters since independence in 1991.
The Kyrgyz government ruled out an act of terrorism, Interfax news agency reported.
Survivors said a fireball engulfed the plane when it came down near Bishkek's main airport at Manas, some 30 km (20 miles) from the Kyrgyz capital.
One told Kyrgyz state television that a strong blast shook the fuselage shortly after he escaped from the burning wreckage: "When my friend ran out, his clothes were ablaze."
Photographs from the crash site released by the state news agency Kabar showed the plane's smoking fuselage and fragments of aircraft strewn over the ground.
Airport employees who saw the wreckage on Sunday said the tail was the only part of the plane still intact.
Flags will fly at half mast on public buildings on Tuesday and shows, theatres and cinemas will close for the day as a mark of respect for the dead, after President Kurmanbek Bakiyev ordered a day of national mourning.
Russian leader Dmitry Medvedev sent his condolences to the tiny Central Asian state after the disaster at Manas, part of which is used by the US military as a base to supply the international force fighting Taliban insurgents in Afghanistan.
The cause of the crash remained unclear, although Prime Minister Igor Chudinov said on Sunday that initial reports suggested the plane had suffered a sudden loss of cabin pressure, causing the pilot to request an emergency landing.
The aircraft, owned by local private carrier Itek-Air, was chartered by an Iranian company.
Members of a teenage basketball team were among the dead and officials said many of the victims were so badly burnt that DNA tests would be needed to identify them.
Only 25 of the estimated 90 people aboard the aircraft, survived -- 14 of them Kyrgyz nationals and 11 Iranians.
The US embassy in Kazakhstan denied two US basketball players, in Kyrgyzstan on a coaching trip, had taken the ill-fated flight.
"They caught a plane home last night from Almaty" in nearby Kazakhstan, an embassy spokesman said.
Transport Minister Nurlan Sulaimanov said the plane, built in 1979, was in good shape and had been inspected only two months ago.
