At least ten NATO oil tankers were torched in southern Pakistani Sindh province early Monday morning while on their way from Karachi to Peshawar, reported local Urdu TV channel Geo.

According to the report, the incident took place at about 2:00 a.m. local time Monday morning when unknown gunmen opened fire at a NATO supply convoy moving from the southern port city of Karachi to Peshawar, a major city in northwest Pakistan, on the national highway near Khairpur, a city in the northern part of Sindh province.

Following the attack, the oil tankers caught fire and four people including three drivers were seriously injured. One hotel and three shops nearby the attack site also caught fire, said police.

Six fire brigades from Khairpur and the neighboring city of Sukkur were called in to put off the fire.

Currently nearly 70 percent of the supplies for the U.S.-led NATO troops in Afghanistan is reportedly shipped through Pakistan via land route. The frequent attacks on NATO supply convoys in Pakistan have created a big headache for the NATO troops in Afghanistan, forcing them to consider opening a new route into Afghanistan from the north though much more inconvenient and costly than the southern route from Karachi.