Senior superintendent of police Paresh Pandey told the BBC Hindi service that at least 30 others had been injured.

The first explosion occurred at a Hindu temple and was followed by at least another blast at a railway station. Police were trying to defuse another bomb.

"The number of bomb blasts is now established at three and the death toll is 12," Varanasi's deputy administrator Kamlesh Pathak told AFP by telephone from the holiest Hindu city, which lies on the banks of river Ganges.

Pathak said 10 people, mainly devotees, were killed at the revered Hanuman Temple shrine when the first blast occurred and two passengers were killed in the second bombing in the Varanasi rail station 10 minutes later.

"The third blast occurred inside a crowded coach of the Shiv Ganga Express minutes before it was to set off for New Delhi," Pathak said.

Varanasi - in the northern state of Uttar Pradesh - is a major pilgrimage centre in India.

The city, about 670 km (415 miles) south-east of the capital Delhi, attracts large numbers of Indians as well as foreign tourists.

A second bomb went off at the main railway station just minutes after the first blast, with eyewitnesses saying they saw a number of casualties.

Police said a team of experts were trying to defuse a third bomb on one bank of the River Ganges.