The Beringia Sled Dog Race covers 601 miles between the remote villages of Esso and Ossora and includes a field of 15 teams.
The Iditarod taking place across the Bering Sea in Alaska has a higher profile, but Russia's RIA Novosti news agency said Guinness World Records has certified the Beringia as the longest mushing trail in the world. The certification came in 1991 and 1992, when the trail was more than 1,200 miles long, compared to the 975 miles of this year's Iditarod.
This year's Beringia trail includes 17 stages and is manicured by snow machines and marked by flags.
Racers can get toasty at night in heated quarters at the checkpoints.