Colombo - At least 37 Tamil separatist rebels were killed in northern Sri Lanka as government troops sought to capture the last remaining rebel-held territory there, and police commandos shot dead 13 more rebels in the south-east, military officials said Friday.

Clashes were reported around the Pudukudirrippu area, 390 kilometres north-east of Colombo, beginning Thursday and continuing into Friday.

Among those killed were the leader and deputy of one of the rebels' brigades, officials said.

Troops said they recovered 37 rebel bodies, but the death toll could be higher.

In south-eastern Sri Lanka, police commandos on Friday shot dead 13 rebels with the Liberation Tigers of Tamil Eelam (LTTE) in a jungle hideout.

A military spokesman said the guerillas were killed in the Lahugala area, 320 kilometres south-east of Colombo.

The area was one of the locations that the government claimed to have cleared of the LTTE during its offensive to eliminate the group, which began in August 2006.

The government has claimed that guerillas were now confined to an area of 21 square kilometres in the north-east, but Friday's incident was an indication that the presence of small groups of rebels could not be ruled out.

The LTTE has been fighting for more than 25 years for a separate state for the Tamil ethnic minority in the northern and eastern parts of majority-Sinhalese Sri Lanka.

Meanwhile, an estimated 55,000 civilians remained trapped in the north-eastern area of Mullaitivu with most of them in an area that the government has declared as a "safe zone" for them.

On Thursday, the UN's World Food Programme sent 1,030 tonnes of rice, wheat, dhal, vegetables, dairy products, vegetable oil and sugar to the civilians there by ship.

The next consignment was due to be sent in three weeks, and Thursday's aid shipment was the biggest to be sent into the rebel-held areas since January. (dpa)