Pakistan has summoned United States Ambassador Cameron Munter to seek clarification over the Nato raid on its military checkpost in countrys nonwestern tribal region. The sources said that Munter has been summoned in protest against the Nato attack that led to killing of 28 security personnel. The Pakistan Army says the death toll stand at 24. The sources said that Pakistan would seek clearance over the attack, which occurred despite a mechanism prepared by Pakistan and Nato forces to avert such incidents. The Pakistans military will take serious action if any Nato attack occurs in its territory in future, said a statement issued here on Saturday.