SLAMABAD: A car bomb outside a gas station in Pakistanâ€™s third largest city killed 20 and wounded more than 100 people on Tuesday, underscoring the reach of Al-Qaeda and Taleban militants in the US -allied nation.The blast badly damaged the station and an office of Pakistanâ€™s state-run airline in eastern Faisalabad city, though the initial target was not immediately clear. The district in the important industrial city is home to commercial, police and government buildings.Islamist militants seeking to overthrow the government have bombed hundreds of police, army, commercial and civilian targets in Pakistan over the past three years.Most have been in the northwest close to the Afghan border where the insurgents are at their strongest.Tuesdayâ€™s bombing apparently caused secondary explosions at the fuel station, adding to the destruction, Faisalabad police chief Aftab Cheema said.TV footage showed piles of bricks, and chunks of twisted metal from cars strewn across the neighborhood. Rescue workers struggled to pull victims out of the rubble.Cheema said 20 people were killed and more than 100 were wounded. â€œThis was a terrorist activity,â€ he said.Faisalabad, 160 miles (260 kilometers) south of Islamabad, is home to Pakistanâ€™s textile industry. Militants have rarely struck there, but it lies in Punjab province, where Islamist extremist groups have deep roots and are believed to be growing in strength.The US has pushed Pakistan to crack down on Islamist extremist groups in its borders, saying they threaten not only Western troops engaged in the Afghan war effort but also the stability of Pakistan itself. The army has launched offensives in the northwest, but questions remain over whether the state has fully severed ties with extremist networks it once supported for foreign policy goals.