Fire rages following attack on NATO oil tankers near Pakistan's southwest city of Quetta on October 6, 2010. At least one driver was killed as some twenty NATO oil tankers were attacked by unknown gunmen early Wednesday morning near Quetta, the fourth such attack in the country since last Friday. [Xinhua/Iqbal Hussain]

At least one driver was killed as some 20 NATO oil tankers were attacked by some unknown gunmen early Wednesday morning near Quetta, a city in southwest Pakistan, reported local media.

Sources in Quetta confirmed to Xinhua on telephone that the attack took place at about 6:00 a.m. Wednesday when some unknown gunmen riding on motorcycles opened fire at a NATO convoy parked at a parking lot some 15-minute ride from Quetta, the capital city of Pakistan's southwest province of Balochistan. The NATO convoy attacked comprised 40 supply trucks, said the sources, adding that the oil tankers catching fire following the attack were parked a little distance away from the other trucks of the convoy and they roughly counted for some 20 units. As the fire caused by the attack on the oil tankers is so huge that it might spread to the others parked nearby, said the sources, adding that help has been asked by Quetta from nearby cities to reinforce its fire brigade to extinguish the fire as the city boasts only a dozen of fire engines.

Wednesday morning's attack on NATO supply trucks is the fourth of its kind since last Friday following a recent air strike by two NATO helicopters within Pakistan's territory, which reportedly killed three Pakistani border soldiers and injured three others.

On Thursday two NATO helicopters shelled a check post of the Pakistani army in Kurram agency in the country's northwest tribal area which borders Afghanistan, causing a strong protest from the Pakistani government over the NATO's violation of its territory right.

The Pakistani side has not only sought explanation, apology and compensation for the incursion from the NATO side, but also ordered a blockade of the NATO convoys which supply goods to the U. S.-led NATO troops in Afghanistan via the land route of Pakistan, which has left hundreds of NATO supply trucks stalled on the road heading towards Afghanistan, making them extremely vulnerable for terrorist attacks.

Early on Friday morning, some 20 militants attacked a NATO convoy with rockets in Shikarpur, a city in the northern part of Pakistan's Sindh province, killing three people and leaving 27 NATO oil tankers completely burnt.

Later on Friday evening, another two NATO supply trucks were attacked by a rocket in the country's southwest city of Khuzdar, during which two people were killed.

On Monday morning, nine militants riding on motorcycles attacked a NATO convoy parked nearby Pakistan's capital Islamabad, leaving 12 people killed and 28 trucks torched.

Following the attacks, Pakistan Taliban claimed the responsibility for two of the three attacks and vowed to launch more attacks on NATO convoys in the country if NATO did not stop its air strikes over the Pakistani territory.

The repeated attacks on NATO convoys have put NATO under heavy pressure as nearly 70 percent of NATO supplies and 40 percent of its fuel are reportedly being shipped through Pakistan to Afghanistan.

Local watchers believe that a comprise is likely to be made on the NATO side facing the pressure from the Pakistani government over NATO's violation of its territory right.