At least 36 people have died in a collision between a methanol tanker and a double-decker bus on a motorway in northern China on Sunday, officials and state media said.

Three of the 39 bus passengers travelling around 2am local time on a highway near Yan'an, Shaanxi province, survived the crash and were being treated in hospital, the official Xinhua news agency said on Sunday.

Yue Jiuxiang, a local traffic police official in charge of the rescue operation, said most of the passengers were asleep at the time of the crash.

"Soon after the collision, the bus was engulfed by flames," he told state-broadcaster China Central Television.

"The front part of the bus was seriously damaged. Also most of the passengers were sleeping. This is why so many people died."

Yue said the bus was en route from Baotou in Inner Mongolia to the Shaanxi provincial capital Xian when the collision occurred.

Police were investigating the cause of the accident which occurred on the Baotou-Maoming Expressway, a motorway that spans the length of China from the northern city of Baotou to the southern province of Guangdong.

Accidents common

Traffic accidents are among the leading causes of death in China, according to public health officials, as new and often poorly trained drivers take to roadways in greater numbers.

State media reports citing police figures say about 100,000 people have been killed in traffic accidents annually over the past decade, with the figure dipping to 70,000 last year.

Buses are also commonly involved in road accidents as operators often seek to cram as many people as they can into their vehicles to maximise profits and drivers hurtle down highways.

Twenty-three people were killed and three injured in April when a bus and truck collided in the eastern province of Anhui.

Another collision between a tour bus and a truck the same month left 13 dead and 21 injured.

Source: Agencies