Guwahati, Feb. 27 :     Bursting out of a deceptive shell, the outlawed United Liberation Front of Asom (Ulfa) today killed a senior minister, Nagen Sarma, by blowing up his car. Ulfa 'chief of staff' Paresh Baruah claimed responsibility for the murder of the public works and forest minister, saying over phone that it was 'an answer' to the joint operations of Indian and Myanmarese forces against the outfit. However, the army has denied that such an operation had been launched. Sarma, who was also the general secretary of the ruling Asom Gana Parishad, was killed in an ambush around 1.45 pm at Nij Banhjani village of lower Assam's Nalbari district, known to be a stronghold of the Ulfa. Though the Ulfa has been lying low for some time, intelligence agencies had alerted the state government last year that three Cabinet ministers, including Sarma, were vulnerable to attacks, especially by the banned organisation. Sarma is survived by his wife and a daughter. The Asom Gana Parishad has called a 12-hour state bandh on Tuesday. In another incident in central Assam's Nagaon district, Lt. Mayeker Mahendra Atma was killed in an encounter with the Ulfa. Three Ulfa activists - Tridip Bhuyan, finance secretary of the outfit's central zone, Rajani Bordoloi and Dhan Bora - were also killed in the shootout. The minister was proceeding towards Dakhin Nalbari College to attend a function when a bomb, planted on the road, exploded and ripped apart his vehicle about 100 metres away from the educational institution. The minister, whose car was the third in a convoy of four, and four others died on the spot. Unconfirmed reports said the rebels, hiding in a bamboo grove, opened fire soon after the explosion. The police have recovered a fuse wire about 100 metres long from the grove. The legs of Sarma, sitting in the rear, were severed, while those in the front seat - bodyguard Sarat Baruah, personal assistant Makhan Barpatra Gohain and driver Mantu Deka - suffered internal injuries. The rebels fled the site of the ambush before other guards could recover from the shock. The police picked up several persons from the area for interrogation. The explosion left behind a crater about 10 feet in diameter and three feet deep. Electric poles and transmission wires in the vicinity were damaged by the impact of the blast. The chief minister, Prafulla Mahanta, who was away in Kokrajhar attending a session of the Bodo Sahitya Sabha, cut short his visit and rushed to the spot of the ambush. The attack 'will not deter the government from its stepped-up offensive against militancy', Mahanta told The Telegraph tonight. The Ulfa's central publicity secretary said in a statement that 'all those who had taken part in the Assam agitation were responsible for the ills plaguing the state today'. Sarma was the general secretary of the All-Assam Students' Union from 1977 to 1979. He was also the adviser to the organisation from 1979 to 1985 - the period of the Assam agitation.