LINK KARACHI (Reuters) - Gunmen in the Pakistani port city of Karachi set fire to two armored personnel carriers (APCs) bound for U.S. forces in Afghanistan, police said on Monday. There have been reports Islamist militants had threatened to start attacking supplies bound for foreign forces in Afghanistan in Karachi, where many supplies arrive before being trucked overland into Afghanistan. The APCs were on a lorry parked by a main road since August 18 because of a strike by truck drivers over rising fuel prices. "They were armed and about two dozen of them. They first fired and then burned the two APCs," senior police official Faisal Noor told Reuters. Noor declined to comment when asked if the attack might have been the work of Taliban supporters trying to disrupt supplies reaching foreign forces in Afghanistan, saying his men were still investigating. From Karachi, supplies for U.S. forces are trucked through two border crossings, one into the southern Afghan town of Spin Boldak, and the other to the northeast at the top of the Khyber Pass. Taliban militants regularly attack supplies, in particular fuel trucks, on the border or after they pass into Afghanistan. But if confirmed, this would be the first militant attack on U.S. military supplies in Karachi.