Colombo: Sri Lanka's military launched a new offensive yesterday against Tamil Tiger rebels in the island's northwest, a military spokesman said.

The operation is aimed at taking control of rebel-held areas south of the northern district of Mannar, Brigadier Prasad Samarasinghe said.

Mannar, about 220km northwest of Colombo, has become a flashpoint in the country's escalating conflict.

"This is a humanitarian mission to liberate some 6,000 people being held in the area," Samarasinghe said. He said the rebels were using the region's 6,000 residents as human shields to protect themselves against military attacks.

A spokesman at the Defence Ministry information centre said the operation had begun only on the ground, and that he did not have more details.