Gunmen torched several NATO oil tankers Monday in Pakistan's Sindh province as the convoy was proceeding to Afghanistan, authorities said. Geo News reported at least 10 trucks were set ablaze by the attackers as the vehicles traveled on the National Highway near Khairpur. The province's capital is the port city of Karachi where the NATO supplies arrive to be taken by road across Pakistan to Peshawar and then across the border to Afghanistan. Geo News reported four people, including three drivers, were seriously injured in the attack. The flames also spread to a nearby hotel and three shops, police said. Traffic on the highway was suspended as a result of the attack, Geo News said. The Pakistani land route is increasingly coming under such attacks, which would force NATO to rely more on the northern routes to supply its troops in Afghanistan.