Pakistani fire fighters try to extinguish fire engulfed NATO oil tankers after militants attacked a terminal in Nowshera near Peshawar, Pakistan on Wednesday, Oct. 6, 2010. [Xinhua]

At least 30 NATO oil tankers were burned following an attack on Wednesday night by unknown gunmen in Nowshera, a city in northwest Pakistan, reported local media.

According to local media reports, unknown gunmen opened fire at dozens of NATO oil tankers stuck in Nowshera due to the blockade of NATO convoys by the Pakistani government over NATO's violation of its territory right by shelling at a Pakistani army check post across the border on Thursday, which killed three Pakistani troops and injured three others.

Sources in Nowshera, a city close to one of the two border passes that NATO convoys have to go through into Afghanistan, told Xinhua that the gunmen fired at the NATO convoy one by one with guns and rocket launches.

Wednesday night's attack is the second of its kind on Wednesday and at least the fifth of its kind since last Friday following an air strike by two NATO helicopters across the Pakistani border.

Earlier Wednesday, Pakistan Taliban militants attacked a NATO convoy in the country's southwest city of Quetta, leaving at least one killed and a total of 22 oil tankers burnt.

While claiming responsibility for four of the five recent attacks on NATO convoys, Pakistan Taliban said the attack is a revenge for the NATO cross-border incursions and stepped-up U.S. drone strikes and it has threatened more such attacks unless the NATO stops cross-border fightings.

The latest attack on NATO convoys came shortly after the U.S. ambassador to Pakistan has reportedly apologized to the Pakistani government for the recent incursions of the NATO forces into the Pakistani territory.

The apology made on Wednesday night by the U.S. ambassador to Pakistan Anne Woods Patterson indicated a softening attitude of the U.S. side towards the pressure exerted by the Pakistani side over the NATO's violation of its territory right.

Prior to this, the U.S. government said that the blockade of the NATO convoys by the Pakistani government would not affect its military operations in Afghanistan. But local watchers believe that the U.S. side has to make a compromise over the issue as nearly 70 percent of the NATO supplies and 40 percent of its fuel are reportedly shipped through Pakistan to Afghanistan.