Calcutta, June 8 :    Calcutta, June 8:  Terrorists are planning to strike Writers' Buildings between June 10 and 15, a Central intelligence report has informed the Buddhadeb Bhattacharjee government. Going public with the intelligence, the state government today threw a huge security shield around Writers' Buildings and intensified the watch on vital establishments and installations. 'We received the alert from the Centre late last night and put into motion all efforts to track these agents down,' said state home secretary A.K. Deb at Writers', where he reviewed the security measures with senior officers. The Central report said several batches of terrorists, who have entered the city fringes, would try to ignite an explosion in the BBD Bag area. Following leads that two batches of terrorists are staying in a Beniapukur house, a city police team raided the place today. Simultaneous raids were also carried out in Colootola Street, Chitpur Road and Metiabruz through the day. Several persons have been rounded up for questioning. The Central alert follows the arrest of three Pakistanis two weeks ago by the state IB, which has been pursuing reports that Pakistan's Inter-Services Intelligence had made inroads in and around the city. IB director R.C. Sharma, who has been monitoring the interrogation of the trio, left for Delhi today to brief the Central intelligence agencies. 'We are trying to find out whether the arrival of these three men had anything to do with the possible Writers' Buildings strike warning,' said an official. Home secretary Deb told a news conference during the day that the government has taken 'enough steps to ensure that these operatives cannot penetrate our security cover. Even if they do, we can match them gun for gun'. With memories of the strike outside the American Center on January 22 still raw, the government, minutes after receiving the information, put the police in Calcutta and the rest of Bengal on full alert. The police also threw a larger ring around the BBD Bag area. More policemen in mufti and mobile patrol units were pressed into the inner and outer rings. The Assembly - now in session - the Governor's house, foreign missions, railway and Metro stations, Calcutta and Bagdogra airports, important bridges and highways were buttoned up during the day. 'We are on the highest alert,' said city police commissioner Sujoy Chakraborty.