By Simon Gardner COLOMBO, June 26 (Reuters) - Sri Lankan troops believe they killed or wounded a dozen Tamil Tiger rebels trying to infiltrate defence lines in the far north on Tuesday, the military said, as the island's main foreign donors meet in Oslo. In the capital, bomb squad officers said they found a 20 kg mine -- like those used as roadside bombs in a series of deadly suspected rebel attacks in recent months -- buried in a residential quarter of the city. The fighting in the northern Jaffna peninsula was the latest in a spree of mortar exchanges and land and sea battles in recent months as a two-decade civil war that has killed nearly 70,000 people since 1983 escalates. "They have tried to infiltrate the defence lines, so we have fired some mortars," said military spokesman Brigadier Prasad Samarasinghe. "Ground troops and intelligence suspect 12 cadres were killed or injured." The mortars fell in Tiger-controlled territory, but there was no immediate comment from the rebels. Fighting is now focused on the north after the military captured the Tigers' eastern stronghold earlier this year. The military says it has nearly driven the Tigers from the east altogether, which would leave the rebels hemmed into the island's far north, where they run a de facto state. RIGHTS ABUSES, MASSACRES Sri Lanka's main foreign donors -- Japan, Norway, the United States and European Union -- are meeting in Oslo to seek ways to halt the war, and diplomats say human rights abuses blamed on the state and its Tamil Tiger foes is a central focus. President Mahinda Rajapaksa's government is under ever-increasing pressure to safeguard human rights and properly probe abuses blamed on state security forces after a series of abductions and massacres blamed on both sides. The International Commission of Jurists -- an international body of lawyers observing an inquiry into a massacre of 17 aid workers last year blamed on security forces -- said overnight evidence had been tampered with and was missing. Diplomats and analysts say Sri Lanka is increasingly at risk of isolation over human rights abuses. The Tigers called on the donors to force the government to stick to the terms of a tattered 2002 ceasefire pact, which is now dead on the ground and which government officials argue was too soft on the insurgents. "I believe the constructive step by the international community is to ... force the Sri Lankan government to implement the ceasefire agreement 100 percent to pave the way for peace talks," Tiger political wing leader S.P. Thamilselvan told pro-rebel Web site www.tamilnet.com in an interview. (Additional reporting by Ranga Sirilal)
