Colombo - Tamil rebels Thursday put up a last-ditch effort to prevent government forces from entering a narrow land strip they still hold in northern Sri Lanka, military officials said.

Fighters of the rebel Liberation Tigers of Tamil Eelam (LTTE) hurriedly put up earthworks in the Karavamulliavaikkal area in Mullaitivu district, 395 kilometres north-east of the capital, but troops captured part of the defence structure after a heavy gunbattle, the army said.

Bodies of dead rebels were scattered around the front line, officials said, but casualty figures were not available immediately.

In a video posted on the ministry's website, apparently recovered from the LTTE, footage shows the rebels forcing civilians to serve as human shields and help in building defence structures.

The Defence Ministry said that the rebels were desperately attempting to hold the government troops back by launching indiscriminate gunfire.

An estimated 50,000 civilians are still being trapped in the war zone, according to UN estimates. However, the government says only 20,000 civilians remain in the area.

The Sri Lankan government refused to heed international calls to halt its offensive to allow civilians to flee, saying this would benefit the LTTE. According to UN figures from April, 6,500 civilians have been killed in the fighting this year.

The International Committee of the Red Cross (ICRC) said it delivered 25 tons of food and medicine to the civilians trapped in the rebel-held area on Friday.

The Sri Lankan military says it is on the final phase of its campaign to crush the LTTE, who have been fighting for an independent homeland for minority Tamils in the north-eastern Sri Lanka for more than 25 years.

The government says it is the presence of civilians in the area that is preventing the army from launching a full-scale assault on the rebels' last stronghold. (dpa)