Myanmar and Bangladesh have agreed to repatriate Rohingya recently displaced by an army crackdown "within two years".

The announcement by the government in Bangladesh is the first clear timeline for a return of hundreds of thousands of refugees.

The agreement, finalised in Myanmar's capital Naypyitaw this week, said the process would be "completed preferably within two years from the commencement of repatriation".

However, there was no announcement of when the process would begin.

It will see Bangladesh setting up five transit camps, which would send Rohingyas to two reception centres on the Myanmar side of the border.

More than 650,000 people have fled violence in northern Rakhine state since the army began a crackdown on rebel fighters, which the United Nations has denounced as ethnic cleansing.

Meanwhile, UNICEF has warned that the already dire humanitarian situation faced by Rohingya children in Bangladesh risks becoming a catastrophe as the cyclone and monsoon seasons approach.