COLOMBO: NC s Sri Lanka's Tamil Tigers on Sunday admitted for the first time that their leader was killed by government forces a week ago as the UN demanded better access for civilians displaced in recent fighting.

Almost a week after the government said its troops had killed Velupillai Prabhakaran, 54, in an ambush, the Tigers' chief of international relations, Selvarasa Pathmanathan, acknowledged that the rebel leader was dead.

"We announce today with inexpressible sadness and heavy hearts that our incomparable leader, the supreme commander of the LTTE, attained martyrdom fighting the Sri Lankan government," Pathmanathan said in a statement.

He seemed to suggest that the Liberation Tigers of Tamil Eelam (LTTE) would try to continue their campaign, saying that Prabhakaran's "final request was for the struggle to continue until we achieved the freedom for his people."

The government, however, has said that the rebels' entire leadership has been wiped out and claimed victory in a decades-long war against the Tigers.

Pathmanathan had on Tuesday told the pro-rebel website Tamilnet that Prabhakaran, the founder and leader of the was "safe and well," prompting the government to broadcast footage of the rebel leader's corpse.

The Tigers' admission came as the United Nations chief Ban Ki-moon left Sri Lanka after touring the island's embattled north and speaking with a few of the 300,000 ethnic Tamils displaced by recent fighting.

Sri Lanka has made it clear that aid workers would not be allowed complete access until rebels hiding among the refugees have been weeded out.

Ban, on a visit to one camp housing 200,000 Tamils, had called for his staff to be given "unhindered access" to those displaced in the decades-long war that ended a week ago.

Ban described the conditions as overcrowded and the detained civilians as "badly in need of food, water and sanitation."

The government responded to Ban's appeal by saying that "as conditions improved, especially with regard to security, there would be no objections to such assistance."

President Mahinda Rajapakse warned of "the likely presence of Tamil Tiger infiltrators among the large numbers who had come to the government areas."

The government describes the camps as "welfare villages" and says it wants to resettle all displaced civilians as soon as possible, but Tamil activists say they are "concentration camps" with inmates penned in behind barbed wire.

During his visit, Ban urged Rajapakse to probe alleged human rights violations committed during the defeat of the Tamil separatists, a joint statement on Sunday said.

The government responded warily to Ban's request, promising only to "take measures to address those grievances."

Between 80,000 to 100,000 people died in years of fighting between government troops and Tamil separatists, who were battling for an independent homeland on the Sinhalese majority island, according to the UN.

The UN High Commissioner for Human Rights, Navi Pillay, has said both the military and the Tigers may have been guilty of war crimes, and campaign groups have condemned the army for indiscriminate shelling of civilians.

The Tigers have been accused of using civilians as a human shield.

Rajapakse has robustly rejected all allegations of war crimes since his troops' victory, which came after he ignored repeated calls by the international community for a ceasefire.