MOSCOW - Russian President Vladimir Putin sent condolences Thursday to Indonesian counterpart Susilo Bambang Yudhoyono over the crash of a Russian aircraft in Indonesia, the Kremlin said.

"I offered my deep condolences over the deaths of Indonesian citizens in the crash," Putin said, asking Yudhoyono to convey his sympathy to the families and friends of the victims.

He also appreciated the Indonesian president's personal contribution to the search operation and launching an investigation into the plane crash.

"I have given necessary instructions to Russian representatives to take a most active part in the investigation jointly with Indonesian partners," Putin said.

Also on Thursday, Russian acting Deputy Prime Minister Dmitry Rogozin said "human factor" might have caused the accident.

The new Sukhoi Super jet 100 commercial aircraft, which was on a demonstration flight in Indonesia, crashed Wednesday and there are fears all the at least 45 people on board may have died.

"There has been no information about survivors," Russia's Foreign Ministry said, adding "the plane was carrying 45 people, including eight Russians as well as citizens of Indonesia, Italy, France and the United States."

Other reports on the number of people on board have varied between 46 and 50.