India train blast kills three

The train was carrying mostly farm labourers

A bomb has exploded on a train in the northern Indian state of Punjab, killing three passengers and injuring at least 25 others.

It should ... not be taken as a revival of militancy in the state

Punjab Chief Minister Amarinder Singh

The Dhanbad express was heading south towards the town of Doraha when the explosion engulfed one carriage in flames and spread fumes through the train.

Rescue workers took about 20 minutes to bring the fire under control.

Police said the fire was believed to have been caused by a crude explosive device and forensic investigations were under way.

But the motive for the attack was still unclear.

Motive unknown

Officials were quoted as saying there was no link between the explosion and recent communal violence in the western state of Gujarat, in which nearly 700 people were killed.

Reports quoted officals and police as saying one person was killed instantly by the explosion, while two died later in hospital.

At least four of the injured were said to be in a serious condition.

Most of the passengers were farm labourers on their way to work.

"It should ... not be taken as a revival of militancy in the state," Punjab Chief Minister Amarinder Singh told the Reuters news agency.

No group has yet claimed responsibility for the blast.

India is on alert for violence between Hindus and Muslims over the disputed holy site in Ayodhya, but there has been no communal violence in Punjab for nearly five years.