Sri Lanka's military launched a new offensive against the Tamil Tigers rebels on the island's northwest, a military spokesman said Saturday. "This operation was launched to liberate areas south of Mannar to neutralize LTTE threat," Brig. Prasad Samarasinghe said, using the acronym of rebel's formal name, the Liberation Tigers of Tamil Eelam. "This is a humanitarian mission to liberate some 6,000 people being held in the area," Samarasinghe said. Mannar is located about 220 kilometers (135 miles) northwest of the capital Colombo.