At least 18,500 Rohingya have fled into Bangladesh in the last six days since renewed fighting broke out between militants and the army in neighbouring Myanmar, the International Organization for Migration said Wednesday.

"As of last night, 18,500 people have come across," from Myanmar's Rakhine State, Chris Lom, the IOM's Asia-Pacific spokesman, told AFP, adding an unknown number of refugees were also still stuck on the Myanmar side of the border.