"We're particularly concerned about the [refugees] in the camps, and getting them out, getting them home," he added.

'De facto prison'

Critics have accused the country's government of keeping Tamil civilians in the de facto prison camps without good reason, but government officials say there may still be fighters hiding among the civilians.

Focus: Sri Lanka
Q&A: Sri Lanka's civil war
The history of the Tamil Tigers
Timeline: Conflict in Sri Lanka
'High cost' of victory over Tigers
Caught in the middle
Pascoe visited the camps in the northern part of the island on Thursday before a planned meeting with Mahinda Rajapaksa, the president, and other officials on Friday.

Colombo has promised to allow 80 per cent of the approximately 280,000 Tamils in state-run camps to return home by the end of 2009, and Western governments and the UN are becoming increasingly aware of the prolonged nature of the process.

Many rights groups have said that those in the camps are living in deplorable conditions and for longer than necessary.

The government has said that it needs to separate possible Tamil Tiger fighters from the internally displaced persons, and clear land mines before resettlement takes place.

Ban and Rajapaksa spoke by telephone this week on human rights issues, political dialogue with the Tamils and accountability for alleged rights abuses committed by both sides during the war.

Ban's sending of Pascoe to Sri Lanka comes amid criticism about his "weak handling" of international challenges.

Ban blamed

The Oslo newspaper Aftenposten published last month what it said was a leaked letter from Mona Juul, Norway's ambassador to the UN, to the country's foreign ministry, accusing Ban of being a "powerless observer".

In video

UN presses Sri Lanka to release Tamil civilians

"At a time when the UN and multilateral solutions to global crises are more needed than ever, Ban and the UN are notable by their absence," the leaked letter said, according to Aftenposten.

"The secretary-general was a powerless observer to thousands of civilians losing their lives and becoming displaced from their homes" in Sri Lanka, the letter said.

It noted that Colombo refused to see Ban while the war was going on "but he was heartily invited - and accepted an invitation - as soon as the war was 'won'", adding that "the moral voice and authority of the secretary-general has been missing".

Pascoe said that "a whole range of human rights issues need to be discussed" with the Sri Lankan authorities.

The fate of two UN employees imprisoned in Sri Lanka since June without charge and accused by the government of collaborating with the LTTE, is also of concern to the world body.

Additionally, a Unicef spokesman was expelled from Sri Lanka recently, being accused by the government of bias towards the Tamils, which the UN children's fund denied.

The LTTE fought for an independent Tamil-minority homeland in the north and east of the island. The conflict left between 80,000 and 100,000 people dead.