Pakistani and American troops exchange fire
Pakistani and American ground troops exchanged fire along the border with Afghanistan on Thursday after the Pakistanis shot at two American helicopters, ratcheting up tensions as the United States increases its attacks against militants from Al Qaeda and the Taliban, who are being sheltered in Pakistan's restive tribal areas.
Pakistan on Monday denied reports that its troops opened fire first, therefore triggering lethal Nato cross-border air strikes that left 24 Pakistani soldiers dead.