Tamil rebels attacked a camp of a rival group in north-central Sri Lanka Sunday, killing at least 15 people and capturing 20 others as violence escalated in the island nation. The camp, located in Kasankulam in North-Central Sri Lanka, was raided in the early hours of Sunday. At least 10 injured cadres of the rival group known as the Karuna faction were found near the camp and admitted to a government hospital in the area, news agency Indo-Asian News Service reported.A regional military wing leader of the Liberation Tigers of Tamil Eelam (LTTE) known as V. Muralitharan alias Karuna broke away from the rebels in 2004 and formed his own group. His group has carried out a series of attacks on the LTTE and has posed a threat to the rebels. The existence of the group and the government making use of it in its military operations has been cited as one reason for the LTTE not returning to the negotiating table, the agency reported.