Trains on railways hit by a powerful earthquake in southwest China had resumed by Tuesday afternoon, except on one line cut off by a landslide, state press said late on Tuesday.

The line going from Chengdu, in quake-hit Sichuan province, to Baoji, in neighbouring Shaanxi, was still inoperational, Xinhua news agency said, quoting Ministry of Railways spokesman Wang Yongping.

The landslide happened in a tunnel in Huixian County in northwest Gansu province, also impacted by the 7.9-magnitude earthquake on Monday afternoon, Xinhua reported.

The tunnel collapsed, causing a fire on a 40-car freight train, which included 13 tankers full of petrol.

The train was still burning on Tuesday, 25 hours after it caught fire.

The railway line also suffered from bridge displacements and damage to the line, Xinhua said.

More than 1,000 workers were repairing the line, but it was not known when trains would resume, the Xi'an Railway Bureau was quoted as saying by Xinhua.

A total of 180 trains had been left stranded on railway lines leading to Chengdu after the quake caused numerous landslides and collapses.

The death toll from the disaster increased to more than 12,000, Xinhua reported earlier.