Pakistani police said on Tuesday that a bomb blast wounded five officers in the country's northwest. Police official Mohammed Ashraf said that the explosion hit a police vehicle when it stopped on a road in Peshawar. He said unidentified assailants planted the bomb in a section of gas pipeline that is under construction. He ruled out the possibility of a gas explosion. Peshawar is the main city in the Pakistani region close to the Afghan border where the Taliban and al-Qaida have established bases. The city has seen rising violence, including attacks on trucks carrying supplies to NATO and US forces on the other side of the frontier.