An unknown number of civil war refugees in Sri Lanka will be allowed to leave military-run camps to live with family members, government officials said Wednesday.

The move comes amid growing international concerns about the treatment of about 300,000 Tamil civilians who have been detained since the 25-year civil war ended in May. The war ended with the crushing defeat of the Tamil Tigers rebel group, the death of their leader and the end of their dream for a separate state.

Rishard Badurdeen, Sri Lanka's resettlement minister, said Wednesday that family members will have to apply for custody of their displaced relatives. Their requests must be verified by a second set of officials and will only be granted if state officials agree that the detainees do not pose a security threat.

He stopped short of saying how many Tamils could be freed.

International rights groups have argued against the way Tamils are being treated by the Sri Lankan government, saying that the military camps are an illegal form of collective punishment. They say that the government is dragging its feet in screening the civilians.

However, officials say they will not release detainees until they are certain they are not rebel fighters and until mines are cleared from their villages, located in the northern tip of the island.

So far, about 5,000 displaced civilians have been allowed to leave the camp. Officials say they hope to resettle 80 per cent of Tamils by the end of the year.

Aid workers have warned about the possibility of worsening conditions at the overcrowded camps once monsoon season starts in October.