Colombo:  Sri Lankan troops killed 11 Tamil separatists in several gun battles across the volatile northern region and police seized a large cache of explosives, authorities said on Wednesday.

The latest fighting in northern and eastern Sri Lanka comes amid government promises to capture the rebels' de facto state in the north and crush the group by the end of the year. But diplomats and other observers say the army is facing more resistance than it had expected.

A Defence Ministry official said the fighting on Tuesday was along the front lines that separate government-controlled territory and rebel territory in the north. He spoke on condition of anonymity because he was not authorised to speak to the media. Army troops killed six guerrillas in the Vavuniya district, just south of rebel-held territory, and in the nearby Mannar district, another five rebels died, the official said.