The Sri Lankan government says it is making gains in an offensive against Tamil Tiger separatists, as soldiers killed 16 fighters in recent battles in the north.

Keheliya Rambukwella, a defence spokesman, rejected any possibility of a ceasefire or peace talks at this stage, saying, on Thursday, that this would only be possible if the Liberation Tigers of Tamil Eelam laid down their arms.

"Surely, definitely, positively we are moving forward and we will not turn at any point," said Rambukwella, who is also minister for foreign employment and welfare.

"Nor we will accept any ceasefire, nor any peace negotiations unless they accept preconditions that have been laid down by the government," he told a weekly defence briefing.

The government is pursuing a strategy to gradually retake the Tiger's northern stronghold and win the 25-year civil war that has killed more than 70,000 people.

In fighting on Wednesday, soldiers killed 16 Tigers and wounded 64, the military said.

Last week, the military said it had entered the northern district where the Tigers' de-facto capital is located.

The Tigers, fighting for an independent state in north and east Sri Lanka for ethnic Tamils, have not issued a comment.