At least six people were killed and nine others were wounded in an overnight attack on NATO tankers here, said police. About twenty-five oil tankers, carrying fuel supplies for NATO forces, were standing at Attock Oil Refinery to fill their own fuel tanks when unknown eight to ten militants opened fire at them after Sunday midnight, said Umer Hayat, senior local police officer while talking to newsmen. He said six people were killed on the spot and nine others sustained serious injuries. "The tankers caught fire, which was extinguished only Monday morning." The police officer added that tankers were completely destroyed in the attack, according to reports of foreign news agencies.