A clip posted on YouTube by the Russian site Lifenews shows former Olympic bobsledder Pyotr Makarchuk parading the torch through a crowd in the city of Abakan when flames suddenly leap from the left shoulder and upper arm of his jacket.
Escorts immediately put out the flames and Makarchuk was not injured, said Roman Osin, spokesman for the Russian Sochi 2014 torch relay, who witnessed the incident on Wednesday.
The flames were caused by drops of liquid gas that fell on Makarchuk's jacket, he said.
Russia is conducting the longest torch relay before any Winter Games: a four-month, 65,000-km journey that will end at the opening ceremony in Sochi on February 7.
The Olympic flame has been to the north pole and Lake Baikal, and cosmonauts took an unlit torch on a spacewalk last month outside the International Space Station.
But the torch has gone out dozens of times, including an incident minutes after President Vladimir Putin handed it off in Red Square on Oct. 6. At other times it has burned too fiercely.
Osin said nobody has been injured by the torch. He declined to say how many times it has gone out.