Two rare Siberian tigers, like this one, died in a travelling circus in Russia this week. (San Francisco Zoo/Associated Press)

Two endangered Siberian tigers and several big jungle cats that were part of a travelling circus in Russia died during a 20-hour truck ride this week, a circus administrator confirmed Thursday.

Veterinarians believe the animals suffocated due to exhaust fumes while inside an enclosed truck, which was heated to counter chilling outdoor temperatures that dipped below –30 C.

Circus officials initially said eight Bengal tigers had died during the trip.

Yevgeny Kudashkin of the Mechta Circus clarified Thursday that seven tigers had died, including a lioness and the two Siberians, during the trip across Siberia to the city of Yakutsk, where the circus was due to perform.

The Wildlife Conservation Society estimates that only 300 Siberian tigers remain in the wild. They are the largest tiger species, weighing up to 270 kilograms.

Russian Prime Minister Vladimir Putin has been drawing attention to their plight. In 2008, he made international headlines when he shot a female tiger with a tranquillizer gun at a nature reserve and helped place a transmitter around her neck as part of a program to track the rare cats.

Later that year, Putin was presented with a two-month-old female Siberian tiger for his birthday. State television showed him at his home gently petting the cub. The tiger, named Mashenka, now lives in a zoo in southern Russia.

Tigers remain a popular attraction in many of the dozens of permanent and travelling circuses in Russia.

With files from The Associated Press