Colombo, Apr. 27 : Sri Lankan armed forces have launched a new assault in the northern war zone despite the Tamil Tigers'' call for a cease-fire.

The rebel TamilNet web site said the military attacked an area in the northeast with heavy gunfire early on Monday even as international protests against the offensive mount, notably in in the Indian state of Tamil Nadu, where the chief minister has gone on an indefinite fast to save what he calls the lives of innocent Lankan Tamil civilians.

The rebel call for a unilateral cease-fire Sunday was described as a joke by the Sri Lankan Government and armed forces, notwithstanding the international pleas to spare the tens of thousands of civilians trapped in the war zone.

Colombo rejected the international appeal and accused the rebels of playing for time as the military stands poised to rout them and end a separatist war that has bedevilled the country for 25 years.

"This is a joke," Defense Secretary Gotabhaya Rajapaksa said of the rebels'' truce offer.

Reports from the region have detailed growing cases of starvation and civilian casualties in recent days.

The United Nations, which says nearly 6,500 civilians have been killed over the past three months, has sent its top humanitarian official on an emergency mission to Sri Lanka to push for a cease-fire.

John Holmes met Sunday with senior government officials to underscore "the urgent need for humanitarian access by the U. N. to the combat zone," U. N. spokesman Gordon Weiss said.

The government barred aid workers from the region when the fighting escalated in September.

Holmes was to head Monday to the northern region of Vavuniya to inspect displacement camps and hospitals that have been overwhelmed by the more than 100,000 civilians who fled the war zone over the past week, a foreign news agency reported.

It also said that British Foreign Secretary David Miliband will visit Sri Lanka with his French and Swedish counterparts on Wednesday to try to mediate on the conflict.

The rebels asked the international community to pressure the Sri Lanka Government to halt its offensive.

Both sides have declared previous cease-fires during the recent fighting, but they did little more than briefly disrupt the war''s momentum because the other side continued fighting.

In a sign that rebel morale is crumbling, 23 insurgents dressed as civilians surrendered to the advancing troops, Army spokesman Brigadier Udaya Nanayakkara said.

Last week, the LTTE''s former media spokesman, Velayutham Dayanithi, known as Daya Master, and an interpreter for its political wing, known only as George - also surrendered.

President Mahinda Rajapaksa''s coalition won a sweeping victory Sunday in a local election seen as a referendum on the war. The government won nearly two-thirds of the vote in the Western Province poll and even secured a majority in the capital, Colombo, long a stronghold of the opposition United National Party, which advocated talks with the rebels.

The governing coalition now controls all eight of the country''s provincial councils. (ANI)