New Delhi - Three people were killed and over 30 injured in a powerful explosion inside a passenger train in India's north-eastern state of Assam on Tuesday, news reports said.

The blast occurred in a carriage of an inter-city passenger train which was stationary at the Diphu railway station, about 300 kilometres east of Assam's main city of Guwahati, IANS news agency reported.

The train was travelling from Guwahati to Tinsukia in eastern Assam.

Police said at least six people were critically injured.

A senior Assam police official was quoted as saying that a powerful bomb had been planted in a carriage and set off by a timer device.

Assam saw a series of deadly blasts on October 30 in which more than 90 people were killed and 300 injured. (dpa)