The UN has raised concerns over the return of hundreds of thousands of Rohingya refugees, who fled a military crackdown in Myanmar's Rakhine State, within the next two years as agreed upon by Bangladesh and Myanmar.

As part of a repatriation deal signed by the two Asian neighbours in November last year, Bangladesh and Myanmar officials at a joint meeting in Naypyidaw on Tuesday agreed on plans to facilitate the return of those displaced since August.

"Much work remains to be done in the context of the Rohingya refugee situation to ensure that any potential returns are voluntary, that they occur in conditions of safety and dignity, and that they are sustainable," said Caroline Gluck, senior public information officer for UNHCR, the UN refugee agency.

"The protection of the Rohingya refugees must be guaranteed both in Bangladesh and upon their return to Myanmar," she told Al Jazeera in an emailed response.

Earlier, Bangladesh's foreign ministry said in a statement that "the repatriation would be completed preferably within two years from its commencement".

"There will be two working groups - one will work on verification process for Rohingya, and the other will facilitate the return of verified refugees to Myanmar," an official in the Ministry of Foreign Affairs, who preferred to remain unnamed, said.

When asked whether the verification process is different from the one outlined in 1992 when a similar crisis had led to another deal being agreed upon, the ministry official declined to clarify, saying the foreign secretary will clarify the issue later.

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Under the arrangement, Bangladesh would possibly establish five transit camps from where returnees would be received initially in two reception centres on the Myanmar side, the statement revealed.

Some 1,550 refugees will be sent back each week, which will add up to approximately 156,000 over a period of two years.

"Myanmar has reiterated its commitment to stop the outflow of Myanmar residents to Bangladesh," the Bangladesh foreign ministry said.

The agreement does not specify when repatriation will commence but outlines providing temporary shelter to returning Rohingya and building houses for them later.

'They will slaughter us'

More than 650,000 Rohingya have fled to neighbouring Bangladesh since August 25, when Myanmar's army launched a bloody crackdown in response to attacks on border posts by the armed group, Arakan Rohingya Salvation Army.

Refugees who crossed the border reported mass killings, gang rapes and arson, prompting the UN and rights groups to accuse Myanmar's army of possible crimes against humanity.

The mainly Muslim minority, who live primarily in Rakhine State, is not recognised as an ethnic group in Myanmar, despite having lived there for generations. They have been denied citizenship and are rendered stateless.

Many refugees living in camps in Bangladesh have also raised fears about returning to Myanmar.

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Abd-us-Salam, who is more than 100 years old, has fled three military crackdowns in Myanmar. He and his wife are currently seeking refuge in Bangladesh's Kutupalong refugee camp.

"There's no point in sending us back to Myanmar because there is no security for us there," he told Al Jazeera.

"They will not allow a single Rohingya to live there," he said.

"They will slaughter us all. Please don’t send us back as bait for the monster."

Taslima Begum, another Rohingya refugee, said she would "rather die in Bangladesh than go back".

"We have been persecuted and brutalised there," she said. "They took all our possessions, crops and cattle."

Safe return

UNHCR's Gluck told Al Jazeera that Rohingya refugees said they would only consider returning if they saw positive developments in relation to their legal status and citizenship, the security situation in Rakhine State and their ability to enjoy basic rights back home.

She said that the causes of the crisis, such as the Rohingya's legal and citizenship status, need to be addressed to ensure peace and security in Rakhine State.

Since the signing of the deal, the UN and rights groups have criticised the repatriation plan, because they believe it does not guarantee the protection of the refugees on return.

Delwar Hossain, director of East Asian Study Centre of Dhaka University, told Al Jazeera on Tuesday that it would be impossible to complete the repatriation process within two years.

"I am sceptical whether they will be able to start the repatriation properly with the Physical Arrangement that was signed between the two countries," he said.

The UN has called the violence against civilians in Myanmar a "textbook example of ethnic cleansing".

The ongoing crisis has been described as the biggest forced exodus of 2017.

Faisal Mahmud contributed from Dhaka