* Some refugees in hiding refuse to leave
* Growing fears that situation could turn violent
* Authorities seen leading away activist asylum seeker
* Some men seen boarding buses
* UNHCR says has reports of use of violence; urges de-escalation (Adds UNHCR statement in new paras 6-7)
By Tom Westbrook and Jonathan Barrett
SYDNEY, Nov 23 (Reuters) - About fifty asylum seekers departed an Australian-run detention camp in Papua New Guinea on Thursday after police moved into the complex, confiscating food, water and personal belongings from the roughly 310 who remained.
The Manus Island centre was sealed off after a three-week standoff the United Nations has called a "looming humanitarian crisis" as detainees defied attempts by Australia and Papua New Guinea (PNG) to close it.
"Right now we have no water," one of the asylum-seekers in the camp said in a mobile telephone message. "I came back to my room and they took my laptop and money and cigarettes."
Video images shot and posted on social media site Facebook by Sudanese refugee Abdul Aziz showed police using a megaphone to tell asylum seekers to leave because their stay at the camp, located on land used by the PNG navy, was illegal.
Men boarded buses in footage he posted later on social network Twitter. The buses took the men to alternative accommodation, three sources said.
In Geneva, the U.N. refugee agency UNHCR said it had received reports of force being used to remove the refugees and asylum seekers and called for calm.
"We urge both governments to engage in constructive dialogue, to de-escalate the tensions and work on urgent lasting solutions to their plight," the U.N. High Commission for Refugees (UNHCR) said in a statement noting it lacked full access to the shuttered facility.
A police blockade of the camp was still in place, Tim Costello, chief advocate of aid group World Vision Australia, said by telephone from outside, adding that he had seen buses leave and that the accommodation he had visited was unfinished.
PNG immigration and police officials did not return telephone calls from Reuters to seek comment.
The camp in PNG, and another on the tiny Pacific island nation of Nauru, have been the cornerstones of Australia's controversial immigration policy, which has been strongly criticized by the United Nations and rights groups.
Australia opened the camps in a bid to stem a flow of asylum seekers making dangerous voyages by boat to its shores.
Under its "sovereign borders" immigration policy, Australia refuses to land asylum seekers arriving by sea, and sends them to the offshore camps instead.
'WE WON'T BE PRESSURED'
At the camp, witnesses said officials in army fatigues led away Kurdish journalist Behrouz Boochani, a resident for four years who posts regular social media messages on conditions there.
Boochani later posted that he had been released after being handcuffed for several hours and had left the camp.
"My understanding is that a number of people, a small number of people, have been arrested, including the individual," Australia's Minister for Immigration and Border Protection Peter Dutton told SKY News, referring to Boochani.
Pictures sent via a messaging service showed upturned boxes of food and torn packets of rice and instant noodles and smashed furniture, including broken beds.
Last year PNG's Supreme Court ruled that the centre, first opened in 2001, breached its laws and fundamental human rights, leading to the decision to close it.
But the asylum seekers say they fear for their safety if moved to a transit centre on the island, and risk being resettled in PNG or another developing nation permanently.
"We don't want another prison. We want to leave this place, but they need to give a good solution for us," the first asylum-seeker said.
"We don't want another prison. We want a third country."
Most of those in the camp are from Afghanistan, Iran, Myanmar, Pakistan, Sri Lanka and Syria.
The transit centres had food, water, security and medical services, Australian Prime Minister Malcolm Turnbull said.
"They think this is some way they can pressure the Australian government to let them come to Australia," Turnbull told reporters in the capital, Canberra. "Well, we will not be pressured." (Reporting by Tom Westbrook and Jonathan Barrett in SYDNEY Additional reporting by Swati Pandey in SYDNEY and Melanie Burton in MELBOURNE and Stephanie Nebehay in GENEVA; Editing by Clarence Fernandez and Toby Chopra)
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