Bangladesh has vowed to block new arrivals and has deported some of those it has caught trying to make the crossing
18,500 Rohingya cross into Bangladesh since fresh Myanmar fighting: IOM
More than 18,000 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 Organisation for Migration said on 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.
Mr Lom said exact figures were difficult to obtain because many of those who have made it into Bangladesh might not register with local authorities.
Bangladesh, which already hosts some 400,000 Rohingya who have fled Myanmar over the years, has vowed to block new arrivals and has deported some of those it has caught trying to make the crossing.
"We also know there are people stuck at the border but we do not know how many," Mr Lom added.
Northern Rakhine has been under lockdown since October last year when a previously unknown group of Rohingya militants ambushed a series of border posts inside Myanmar.
That prompted a massive military response, leading to some 87,000 Rohingya fleeing to Bangladesh, bringing with them harrowing tales of murder, rape and burned villages.
The UN believes the Myanmar government's response to the crisis may amount to ethnic cleansing and crimes against humanity.