At least six passengers were killed and more than 20 injured yesterday after an express train derailed in eastern India's Bihar state, officials said.

Nine coaches of the Delhi-bound Seemanchal Express came off the tracks early yesterday near Sahadai Buzurg station, about 30 kilometres (20 miles) east of the state capital Patna.

"Six people have died and nearly 24 have been injured," Indian Railways spokesman Rajesh Kumar told AFP.

Most of the travellers were asleep when the train travelling at 55 kilometres (34 miles) an hour came off the tracks around 4:00 am (2230 GMT Saturday).

"I was sleeping and suddenly there was a big bang and found myself under a pile of bags," passenger Mahesh Kumar told reporters.

A "rail fracture" caused the accident, Indian Railways said in a statement after an initial investigation. The company promised a thorough probe of the accident, which came days after the Indian government said it had improved rail safety.

Cash compensation of 500,000 rupees ($7,000) would be given to the relatives of those killed, the railways ministry said.

Railways minister Piyush Goyal on Friday had claimed to have improved rail safety after a series of deadly accidents spooked the country.

Goyal told parliament that all unmanned rail crossing had been eliminated, one of the main causes of train collusions in India.