PESHAWAR/ISLAMABAD NATO helicopters and fighter aircraft attacked two Pakistani military checkpoints along Afghan border in a pre-dawn attack on Saturday, killing up to 26 troops and prompting Pakistan to shut vital supplies to NATO/ISAF troops, besides lodging strong protests with the US and NATO authorities. A major and a captain were among the martyred troops and about 11 others were wounded in the attack that came around 2am at two mountaintop checkpoints, about 2.5 km from the border. About 40 Pakistani army troops were stationed at the outposts at Selala, a suburb of Balezai region in Mohmand Agency, and sources in political administration suggested the casualties had reached 28. The attack is the worst single incident of its kind since Pakistan uneasily allied itself with Washington after Sept 11, 2001 attacks. The reaction from Pakistan military as well as the civilian government at this apparent provocation was strong and prompt, and they sent a clear message that no such action at any pretext was acceptable to Pakistan. An ISPR statement released Saturday said that Pakistani troops effectively responded immediately in self-defence with all available weapons. The press release said a strong protest has been launched with NATO/ISAF in which it has been demanded that strong and urgent action be taken against those responsible for this aggression. The incident occurred a day after US General John Allen met Pakistani Army Chief of Army Staff General Ashfaq Pervez Kayani to discuss border control and enhanced cooperation. Strongly condemning the attack, Gen Kayani said that the NATO/ISAFs 'blatant and unacceptable aggression resulted in loss of precious lives of Pakistani soldiers, according to the ISPR press release. While lauding the effective response by the soldiers of Pakistan Army in self-defence, he directed to take 'all necessary steps for an effective response to this irresponsible act. A senior Pakistani military officer said efforts were under way to bring the bodies of the slain soldiers to Ghalanai, the headquarters of Mohmand tribal region. "The latest attack on our post will have serious repercussions as they (NATO troops) without any reason attacked our post and killed soldiers asleep," he said. Foreign Office Spokeswoman Tehmina Janjua in a condemnatory statement said: "Prime Minister Yousuf Raza Gilani has condemned in the strongest terms the NATO/ISAF attack on the Pakistani post. On his direction, the matter is being taken (up) by the foreign ministry in the strongest terms with NATO and the US." PM Gilani cut short a weekend visit to his home town to return to Islamabad to hold crisis talks with President Asif Ali Zardari and Army Chief Gen Ashfaq Pervez Kayani, state TV reported. He also talked over phone with President Zardari, COAS Kayani and Foreign Minister Hina Rabani Khar to discuss the crisis situation. On the instructions of the prime minister, Foreign Secretary Salman Bashir on Saturday called in US Ambassador Cameron Munter to lodge a strong protest. The secretary conveyed to the US ambassador that the unprovoked attack by NATO/ISAF copters on border post had deeply incensed the government and the people of Pakistan, a press statement issued by the Ministry of Foreign Affairs said. The president, prime minister and the government of Pakistan strongly condemns the attacks which were totally unacceptable, constituted a grave infringement of Pakistans sovereignty, were violative of international law and a serious transgression of the oft conveyed red lines and could have serious repercussions on Pakistan-US/NATO/ISAF cooperation, the statement said. The ambassador was informed that the prime minister had convened an emergency meeting of the Defence Committee of the Cabinet to evaluate the situation arising from these uncalled for attacks by NATO/ISAF forces. Strong protest has also been lodged in Washington and at the Nato Headquarters in Brussels, the statement added. This apparent provocation is expected to further worsen US-Pakistan relations, which are already at one of their lowest ebbs following a tumultuous year that saw the jailing and then release of a CIAs Raymond Davis, and the killing of Osama bin Laden by US special forces in a clandestine raid in May. Pakistan called that raid in Abbottabad a flagrant violation of its sovereignty. Munter expressed regret for the loss of life in the unfortunate incident. In a statement issued by US embassy, Munter said: I have seen press accounts of an incident on the Pakistani-Afghan border in which Pakistani soldiers were reportedly killed. I regret the loss of life of any Pakistani servicemen, and pledge that the United States will work closely with Pakistan to investigate this incident. The commander of NATO-led forces in Afghanistan, General John R Allen, said he had offered his condolences to the family of any Pakistani soldiers who 'may have been killed or injured during an 'incident on the border. A spokesman for the force declined further comment on the nature of the 'incident and said an investigation was proceeding. It was not yet clear, he said, whether there had been deaths or injuries. When contacted by this newspaper, the Nato (North Atlantic Treaty Organisation) Air Operations Spokesperson in Kabul Christopher DeWitt 'regretted' the loss of lives in the incident. Declining to give details of the number of Nato helicopters involved in the aerial attack, the spokesman said the matter was being probed. "It is a sad day for everyone. The Nato regrets the loss of lives of Pakistani military men and offers condolences with the families who have suffered from this tragedy." Asked if Nato offered an apology to Pakistan over the seemingly unprovoked attack, DeWitt said, "We deeply regret this incident." When insisted if an apology was rendered, an audibly irritated DeWitt dropped the call.