SEOUL - NORTH Korea's prison camps hold about 300,000 people and authorities hold annual mass executions of inmates seen as defiant, a new group formed by defectors said on Tuesday.

Torture and sexual violence are also rampant at the camps, said Mr An Myong-Chul, a 40-year-old former camp guard who defected to South Korea 10 years ago.

'Every year at around this time North Korea executes up to 20 inmates at each camp,' he said at a ceremony to launch a group called the Campaign for North Korean Freedom.

An heads the campaign, supported by about 120 defectors and South Korean activists who work for the release of political prisoners in the hardline communist state.

Freedom House, a US watchdog, estimated in its 2007 report that about 200,000 prisoners were in the camps.

The report was based on old figures, Mr An said, adding that the number of inmates has increased to about 300,000 and reflects 'growing political instability' in the North.

He said he obtained updated information from other defectors.

'As a guard, I was trained to kill all the inmates in an emergency. (Apart from those executed) they are subjected to forced labour until their death,' he said.

Defector Im Jong-Su, 43, said he was held at Camp Number 18 in the riverside village of Kaechon in South Pyongan province, just because his father had been a South Korean soldier captured during the 1950-53 conflict.

South Korea says the North never sent home more than 500 prisoners at the end of the war. Im was born in the camp and escaped to South Korea in 2004.

Mr An's group described North Korea as 'a giant gulag' and called for international cooperation to improve its human rights.

'Especially, women and children held at camps for political prisoners are under extremely severe conditions,' the group said in a statement.

The US State Department's 2007 report on human rights said an estimated 150,000-200,000 people were believed held in political prison camps in remote areas.

Such 'political' offences could reportedly include sitting on newspapers bearing the picture of founding president Kim Il-Sung or current leader Kim Jong-Il, it said. -- AFP