COLOMBO: Sri Lanka's Tamil Tigers have admitted for the first time that their leader was killed by government troops a week ago, but the remants of the rebels appeared split over the future of their struggle.

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 Sunday.

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."

And in a telephone interview with the BBC, Pathmanathan said the Tigers would now use non-violent methods.

"We have already announced that we have given up violence and agreed to enter a democratic process to achieve the rights for the Tamil (self-) determination of our people," he said.

The government has said that the rebels' entire military and political leadership has been wiped out, and last week claimed total victory in a decades-long war against the separatist army.

It is now unclear who is in charge of the LTTE -- with the pro-rebel Tamilnet website signalling a power struggle was in progress.

It said the LTTEs "Department for Diaspora Affairs (DDA)" had declined to comment on Pathmanathan's statement without "explicit authorisation from the LTTE leadership."

Tamilnet also reported that the "Intelligence department of the Tigers reiterated on Sunday that the LTTE leadership is safe and it will re-emerge when the right time comes."

The statements 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.

Ban, on a visit to one camp housing 200,000 Tamils, called for his staff to be given "unhindered access" -- challenging a Sri Lankan government block on aid worker access until rebels allegedly hiding among the refugees had been weeded out.

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.