Investigation underway after Nato strike kills Pakistani soldiers

Washington's relations with Islamabad have sunk to new lows this year after Osama bin Laden was found hiding inside Pakistan and an American contractor working for the CIA shot dead two men in Lahore.

Yusuf Raza Gilani, Pakistan's prime minister, said he had ordered the foreign office to complain to Nato and the United States "in the strongest terms".

Within hours of the attack, police had begun to halt Nato convoys carrying fuel and equipment on a vital supply route to coalition forces fighting inside Afghanistan.