Acting swiftly, the Centre on Saturday rushed additional paramilitary forces to beef up security in Assam after United Liberation Front of Asom militants triggered a powerful blast in Guwahati that left seven persons dead and 30 injured.

The Union home ministry directed the state government to remain vigilant and ensure that nothing untoward happens, a ministry spokesman said.

Home Minister Shivraj Patil strongly condemned the blast, which occurred on the eve of Tarun Gogoi government's completion of one year in office.

While Home Secretary Madhukar Gupta rang up the state Chief Secretary to take stock of the situation, the special secretary (Internal Security) in the home ministry spoke to the state police chief.

The home ministry's statistics show a spurt in ULFA violence in Assam in recent months with the militants resorting to kidnapping, extortion and blasts after the failure of the peace initiative.

While the number of incidents had doubled in the first quarter of 2007 against the corresponding period last year, civilian casualties registered over three-fold increase in the state.

The report said that till March 31, 2007 there have been 156 incidents in Assam compared to 85 during the same period last year.

Likewise, 99 civilians were killed during the first three months this year, which was more than three times compared to the figure of 31 during the corresponding period of 2006.

It said ULFA, with which the government observed over a month-long ceasefire last year but called it off following the outfit's refusal to come to the negotiating table, accounted for over 50 per cent of the violent incidents in 2006.

In the first quarter of 2007, ULFA militants unleashed large scale violence ahead of the National Games in Guwahati in February and in the first two weeks of January they killed 70 Bihari migrant workers.