A suicide attacker struck at the heart of Pakistan’s anti-terrorism operation today targeting military intelligence officials as politicians were briefed on the battle against violent extremists.

Witnesses and police officials said the bomber rammed his explosive-laden car into a four story residential block at the headquarters of the Anti Terrorist Force in the Islamabad suburbs injuring up to seven people. The vehicle had passed through a high security cordon to carry out the second terrorist attack in the Pakistani capital in three weeks.

Last month, 53 people were killed and hundreds more injured in a truck bomb attack on the Marriot Hotel inside a supposedly safe zone.

The security was supposed to be particularly tight in Islamabad today with thousands of army and paramilitary troops deployed in the city and helicopters patrolling the sky all day. Security forces were on high alert because members of parliament were attending a briefing on the military campaign against Islamic militants in northern Pakistan and lawless tribal region on the border with Afghanistan.

No-one has claimed responsibility for the bombing, but investigators suspect Islamic militants were involved. Pakistani security officials said the recent violence could be a retaliation against operations in the Bajaur tribal area, which Pakistani and Western intelligence officials believe has become the main centre of al-Qaeda and Taleban activities.

The militants have also been targeting senior political leaders. Last week, a suicide bomb attack on the residence of a member parliament in Bhakkar district in central Punjab killed more than 30 people.

Thousands of soldiers are involved in the most intense fighting against the militants since Pakistan pledged to join the American “war on terror” in 2001. Military officials said that more than 1,000 people have been killed in the operation over the last eight weeks, but there has been no let up in the hostility.

President Asif Ali Zardari said terrorist attacks would not affect his government’s resolve to fight the militants.

In a rare joint briefing, members of both houses of parliament were brought together for a frank assessment of the security situation. The government said the debate could help generate a consensus on anti-terror policy.

The ongoing military operation and Pakistan’s alliance with the United States have divided the Muslim nation of 160 million. Most opposition parties have called on the government to stop military campaign and negotiate peace with the Islamic militants.

Increasingly common US aerial attacks against suspected Taleban and al-Qaeda hideouts inside Pakistan have further fuelled anti-American sentiments.

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