Islamabad , Pakistan ( CNN ) -- Armed militants on motorcycles in southwest Pakistan ambushed and set ablaze a convoy of tankers contracted to NATO forces in Afghanistan on Sunday night , police said . The gunmen opened fire after forcing the convoy of eight oil tankers to stop in an area 90 kilometers ( 55 miles ) southwest of Quetta , the capital of Balochistan province , police official Abdul Qadir said . The militants killed one of the truck 's drivers and set the tankers on fire before they escaped , Qadir said . Fuel and supply trucks contracted to supply NATO have been left stranded in Pakistan by Islamabad 's decision to block its two NATO supply routes to Afghanistan . Pakistan closed the routes to protest a NATO airstrike that killed 24 Pakistani soldiers last month . The airstrike plunged Islamabad and Washington into one of their worst diplomatic crises ever . In a television interview on Sunday , Pakistan 's Prime Minister Yousuf Raza Gilani said the blockade of Pakistan 's NATO supply routes could continue for weeks until `` new rules of engagement '' were established with Washington . The blockade leaves stranded supply trucks vulnerable to militants in Pakistan who have increasingly targeted the convoys in an effort to undermine the NATO mission in Afghanistan . Sunday 's attack was the second of its kind in four days . On Thursday , militants armed with rocket-propelled grenades and automatic weapons attacked and destroyed more than 20 NATO-bound oil tankers just outside Quetta . Roughly 40 % of supplies for NATO operations in Afghanistan traveled through Pakistan before the supply routes were shut down .
Gunmen on motorcycles force the convoy to stop and then open fire . one driver is killed , police say . Pakistan closed NATO supply routes into Pakistan after an airstrike killed Pakistani . The airstrike prompted a diplomatic crisis between Afghanistan and Afghanistan .