Terrorism across India will continue as long as Pakistan does not end "its mischief" through the Inter Services Intelligence in places like the north-east, National Democratic Alliance convenor George Fernandes said on Thursday.

In a letter sent to Prime Minister Manmohan Singh [Images], Fernandes referred to the deteriorating law and order situation in Assam and claimed that Pakistan's Inter-Services Intelligence "is behind what all is happening in Assam" and the other north-eastern states.

"The state government (in Assam) is aware of everything that is happening. When I was there the last time the chief minister stated in so many words publicly that the mischief-makers are the ISI. That is the truth," he said.

Fernandes asked the prime minister to take up the matter with Pakistan and warned if this was not done, the country would face bigger problems in the north-east than those it was facing in Jammu and Kashmir.

"The kind of terrorism that is going on in India will last as long as Pakistan does not end its mischief in our country through the ISI. You should have a final word on this with the dictator of Pakistan," he told Dr Singh in his letter.

Fernandes said he had decided to take up the matter after two separate delegations of political leaders and traders from Assam called on him to discuss the prevailing situation in the state.