Some 19,000 of the refugees are now staying in Bhashan Char island
Bangladesh wants to send more than 80,000 Rohingya refugees to Bhashan Char facilities after sealing an agreement for the United Nations.
Some 19,000 of the refugees have already relocated from Cox's Bazar to Bhashan Char, despite doubts raised by aid groups.
Bangladesh refugee commissioner Shah Rezwan Hayat said that tens of thousands more would go once the monsoon storms end in November. "We are aiming to relocate some 81,000 [Rohingya] to Bhashan Char by the end of February to complete the 100,000 quota," he told AFP.
The government has spent about $350 million building shelters on the 53 square kilometre (20 square mile) island which was formed by tidal silt deposits about 20 years ago.
Some Rohingya groups alleged that people were forced to go to Bhashan Char, which is 60 kilometres (37 miles) from the Bangladesh mainland.
More than 850,000 Rohingyas have been living in camps in Cox's Bazar since they fled a Myanmar military clampdown in 2017 that the UN says could be genocide.
Bangladesh has been praised for taking in the refugees who poured across the border. Meanwhile, the government has engaged the international community to help press the Myanmar government to take them back.
UN confirms deal
While a Bangladesh security intelligence agency is responsible for relocating the refugees, the government denies that any coercion has been used.
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Still, several hundred Rohingya have fled Bhashan Char only to be detained on other islands or in coastal villages. Dozens died after a fishing boat packed with Rohingya trying to flee the island sank in August.
The UN had expressed doubts about the relocations. But Bangladesh and UN officials said a deal has been agreed to give the UN a role in providing humanitarian assistance and monitoring conditions on the island.
"We can confirm that the UN will sign a memorandum of understanding with the government to protect Rohingya refugees in Bhashan Char on Saturday," a spokesperson for UNHCR told AFP.
Refugee commissioner Hayat said the UN would play a bigger role on the island than they do now in the mainland refugee camps, where they already have extensive operations.
He said: "Bhashan Char residents will receive similar treatment, humanitarian response-wise, to what is now provided to people in the Cox's Bazar camps."
He added that there would also be greater opportunities for Rohingya to work on the island than there are now in the rigidly policed camps.
But Amnesty International raised new concerns over the relocations and highlighted the attempts made by refugees on the island to get away again.
"Some refugees have drowned at sea and many are either being arrested, detained, or forcibly returned to the island," Saad Hammadi, Amnesty's South Asia campaigner, told AFP.
He said Bangladesh, the UN, and donor countries should "develop a rights-respecting policy and ensure the participation of Rohingya refugees in decisions that affect their lives."