STOCKHOLM (AFP) UN Chief Ban Ki-moon and the foreign ministers of Sweden and Denmark were delayed arriving at a conference in Kabul after a rocket attack on the Afghan capitals airport, officials said Tuesday. Swedens Carl Bildt said on his blog that a plane carrying him and Ban was diverted to the main US base at Bagram and then flown by helicopter to Kabul shortly before the meeting featuring around 40 ministers. Danish Foreign Minister Lene Espersens aircraft was meanwhile forced to reroute to neighbouring Kazakhstan, where it was still awaiting permission to try to fly to Kabul again, his secretary said. Bildt said it was always likely that militants would try to disrupt the very important conference, at which Afghan President Hamid Karzai later sought to show that his government could assume full leadership by 2014. Our participation here in the centre of Kabul is proof of our support for the peace process and the stabilisation of the country, he added. But we will be there for the opening of the conference. Basically this rocket attack represents little except for a serious attack on our nights sleep, he said. Afghanistans interior ministry said two rockets landed near the airport overnight but caused no casualties. Kabul was locked down in a massive security operation, patrolled by thousands of Afghan and NATO soldiers to guard against Taliban attack on what has been billed as the largest international conference ever held in Kabul. NATO troops said they killed several insurgents preparing to attack the Kabul conference. The alleged militants were killed during a raid on a house on the southern edge of the city overnight, NATOs ISAF said, suspecting the Taliban of plotting an attack on the conference. Two other militants were captured while pursuing a Taliban facilitator believed to be in final stages of preparation for attacks against the Kabul conference, it said. Automatic weapons and ammunition were impounded, the military said. ISAF had already said that others had been captured elsewhere in the city last week also said to be plotting attacks on the landmark meeting.