A suicide car bomb attack hit a police checkpoint on the outskirts of Peshawar before dawn Wednesday, killing four police and wounding 11 people, including a woman and a cleric. Wednesday's attacker struck the checkpoint in Pir Bala village, on the main road from Peshawar, Pakistan's northwestern capital, to Mohmand, one of seven districts in the Al-Qaeda and Taliban-infested tribal belt. The force of the explosion destroyed the simple, one-storey mud-brick building at the police post, damaged a nearby house and a mosque, police said. "A suicide bomber ploughed his explosives-laden car in Pir Bala police post," Peshawar city police chief Liaquat Ali told reporters. "Four policemen were killed and 11 other people wounded. Two policemen are in a critical condition," he told AFP. Those who were killed had been on duty at the checkpoint at the time of the attack, between 4:30 and 5 am, said police official Mussarat Khan. "The small building at the police checkpoint was destroyed. A nearby house and a mosque were also damaged," he said. Peshawar, with its bustling markets and as a regional headquarters for government and security forces, has been on the front line of deadly attacks. The teeming city runs into the tribal belt, which Washington calls the most dangerous place on earth and a global headquarters of Al-Qaeda. Ali told reporters that the bomber intended to strike elsewhere in the city of 2.5 million and only detonated his vehicle when he was stopped. Pir Bala straddles Warsak Road, which links Peshawar to the mountains of the tribal badlands. This area became a stronghold for hundreds of extremists who fled Afghanistan after the US-led invasion in late 2001. Mohammad Gul, a police official on duty at Peshawar's Lady Reading Hospital, confirmed the death toll and said a cleric and a woman were among the wounded. Siraj Ahmad, a local administration official in Peshawar, said five civilians were among the 11 people wounded. A campaign of suicide and bomb attacks has killed nearly 3,300 people in less than three years across the nuclear-armed country of 167 million. The attacks are blamed on Al-Qaeda, Taliban and other extremist Islamist groups. On April 17, two suicide bombers dressed in burqas killed 42 people when they attacked a crowd of displaced people collecting aid handouts in the Kacha Pukha camp in northwest Pakistan. In perhaps the most audacious recent assault, at least three security officials were killed when militants armed with guns, grenades and two car bombs targeted the heavily guarded US consulate in Peshawar on April 5. Under US pressure, Pakistan as of last year significantly increased air and ground offensives against homegrown militants in the tribal belt. But the rugged region is also routinely hit by US drone attacks targeting Al-Qaeda-linked and Taliban commanders. More than 880 people have been killed in nearly 100 drone strikes in Pakistan since August 2008. The bombing raids fuel anti-American sentiment in Muslim Pakistan and draw public condemnation from the government.