The family of an Irish journalist detained in Cambodia has called on the Government to help secure his release.
Mr Kevin Doyle, the editor of English-language newspaper The Cambodia Daily, was arrested in the eastern province of Mondol Kiri and is being held in a remote area.
He was detained along with an interpreter, an aid worker and another journalist on Friday after trying to track down Christian refugees fleeing to Cambodia from Vietnam.
His brother Robert said the family only discovered what had happened this morning.
"His wife called us from Phnom Penh earlier today, she had only just found out," he said.
"We are very worried about him, we have no idea exactly where he is or what could happen to him. All we know is that the Ministry have him."
He said Kevin, who is from Dublin but moved to Cambodia in 1998, had been writing about the plight of Vietnamese refugees for the last two months.
The stories have been published despite being critical of the Cambodian authorities, which have reportedly denounced the three men for interfering in the situation.
"It is obviously embarrassing for them," Mr Robert Doyle added. "He was writing about this issue for various newspapers. Then, the next thing we know, he is arrested."
The family has contacted Amnesty International which is trying to get further details from the Cambodian Government.
More than 180 Vietnamese hill tribe people, commonly called Montagnards, have been rescued from the jungle over the past week by UN staff and local authorities.
Foreign Affairs Ministry Secretary of State Long Visalo denounced the three men for allegedly interfering in refugee affairs, saying the UN refugee agency was the only group allowed to deal with the Montagnards.
RFA and The Cambodian Daily, with the help of local human rights groups, have been reporting aggressively on the situation of the Montagnards, which the government has sought to play down.
The Cambodia Daily publisher Ms Bernie Krisher said Mr Doyle, an Irish citizen, had been "covering important developments surrounding the Montagnards' appeal for asylum to the UN High Commissioner for Refugees."
He said Mr Doyle's assignment was in the interests of a free press as guaranteed by Cambodia's constitution, and called for "the police to release Mr Doyle on the spot along with his equipment and permit him to continue his work."
A spokeswoman from the Department of Foreign Affairs confirmed they had been alerted to the incident and were investigating the matter.
The Cambodia Daily is an independent daily newspaper based in the capital Phnom Penh.