NATO-led forces claim that they have killed more than 50 insurgents on Pakistani soil across the border from Afghanistan. A spokesman of International Security Assistance Force (ISAF) on Monday said, NATO helicopters crossed into Pakistani airspace from Afghanistan in pursuit of insurgents over the weekend. They followed an attack by insurgents on an Afghan security outpost in the eastern province of Khost. Isaf said no civilians were killed in the operation, but this has not been independently confirmed. Pakistani officials are yet to comment on the raids.Pakistani Interior Minister Rehman Malik has described as violation of the country's sovereignty the NATO helicopters air strikes into Pakistan, which reportedly killing more than 50 militants. He was responding to an agitated senator from the main opposition Muslim League-Nawaz party on the issue in the upper house of the parliament today. Meanwhile, a foreign ministry spokesman said these incidents are a clear violation and breach of the UN mandate under which ISAF operates. He said ISAF/NATO has been asked not to participate in any military action that violates the UN mandate and infringes upon Pakistan's sovereignty.A NATO spokesman in Afghanistan said that the air strikes into Pakistan were carried out after the militants attacked a small Afghan security outpost near the border. The spokesman justified the rare NATO strikes based on the right of self-defense.