The repatriation of hundreds of thousands of Rohingya Muslims who fled violence in Myanmar will not begin as planned, Bangladesh said on Monday, with authorities admitting “a lot of preparation” was still needed.

Bangladesh had been due to start the huge process on Jan 23, after agreeing a two-year time frame with Myanmar.

But Bangladesh’s Refugee Relief and Repatriation Commissioner Mohammad Abul Kalam announced on Monday there was much more work to be done.

“We have not made the preparations required to send back people from tomorrow. A lot of preparation is still needed,” Kalam said.

Since August last year around 688,000 Muslim Rohingya have escaped over the border into Bangladesh in the wake of a military-led campaign in Rakhine state that the UN says amounted to “ethnic cleansing”.

They poured into ill-equipped and overcrowded camps, bringing with them harrowing tales of rape, murder and torture at the hands of Myanmar’s feared army or Buddhist mobs.

After a global outcry, which included loud criticism of Myanmar’s civilian leader Aung San Suu Kyi, the two countries agreed earlier this month that the refugees would be returned to Myanmar in a process they said would take around two years.

Rights groups and the UN have said any repatriation must be voluntary. There are reports that many Rohingya settlements have been burned to the ground.