Sri Lankan security forces went on high alert as leaders began arriving for an important regional summit on Friday, after soldiers killed 21 Tamil Tiger rebels in clashes in the island's north, the military said. Indian Prime Minister Manmohan Singh was among the first to arrive for the eight-nation meeting in the capital Colombo over the weekend. He was followed soon after by Pakistani counterpart Yousaf Raza Gilani. Terrorism and food and energy security are among the issues to be discussed. Some 19,000 extra police and soldiers have been deployed in Colombo but fighting with Liberation Tigers of Tamil Eelam (LTTE) rebels continues in the north. A military spokesman said soldiers killed 21 Tamil Tiger rebels and wounded 21 more on Thursday. “The fighting had also killed 2 soldiers and injured three others,” the spokesman told reporters. Security has been beefed up for the July 27-Aug. 3 South Asian Association of Regional Corporation (SAARC) summit. The SAARC groups Afghanistan, Bangladesh, Bhutan, India, the Maldives, Nepal, Pakistan and Sri Lanka. The Tamil Tiger rebels had declared a 10-day unilateral truce starting from July 26 as a goodwill gesture for the summit but it was dismissed by the government, who said it had not received official notification and was sceptical about the declaration. Sri Lanka's government wants to gradually retake the Tiger's northern stronghold and win the 25-year civil war with an almost-daily barrage of land, sea and air attacks.