The bomb concealed inside a parked scooter exploded near the barracks of a police commando unit and a paramilitary complex in Imphal, the capital of Manipur state, city police chief Radheshyam Singh told AFP.

'Eleven people died on the spot and three succumbed to their injuries in a hospital,' Mr Singh said by telephone from Imphal, adding that the explosion occurred at 7.45pm local time (10.15pm Singapore time).

'One hospital has admitted 15 (injured) blast victims and many more have been taken to other hospitals and we are now trying to find out how many people (in total) are injured,' he said.

'The bomb was kept in a parked scooter and it was powerful in nature,' the police chief said, adding that the victims were all civilians.

The Press Trust of India reported 17 people were killed and more than 30 injured, and said 'unidentified militants' were responsible.

Indian troops and the police sealed off Imphal's borders with adjoining towns and launched a manhunt for the bombers, officials said.

The blast came two days after unknown guerrillas carried out a grenade attack outside the fortified home of Manipur Chief Minister Okram Ibobi Singh also in Imphal city. No one was injured in that explosion.

No one has claimed responsibility for Tuesday's attack, but 19 rebel groups in Manipur are spearheading separate campaigns pressing for changes ranging from homelands for tribal groups to the repeal of a draconian anti-terror law.

'Today's attacks appear to be the handiwork of a tribal (militant) group which we are jointly targeting,' a senior police official said from the neighbouring state of Arunachal Pradesh, without elaborating.

Earlier this month, five people were injured in an explosion during a Hindu festival in Guwahati, the largest city in Assam state which adjoins Manipur.

At least 50,000 people have lost their lives in insurgency-driven violence in six of India's seven northeastern states since the country's independence from the British in 1947.

The militants say the northeast has been largely neglected by India's political leaders, accusing them of focusing only on the development of the country's relatively-wealthier eight northern states.

A steady infiltration of migrants from neighbouring Bangladesh is another major cause of friction between ethnic tribal groups and Muslim settlers from across the two nations' porous borders, analysts say. -- AFP