At least 10,000 Rohingya have entered Bangladesh in recent weeks said the United Nations on Wednesday.
"Based on reports by various humanitarian agencies, we estimate that there could be 10,000 new arrivals in recent weeks," said Vivian Tan, a spokeswoman for the UN refugee agency in Bangkok the Bangkok Post reported.
"The situation is fast changing and the actual number could be much higher," Tan added.
The Myanmar army has carried out a bloody crackdown in the western state of Rakhine, forcing some 30,000 people to flee their homes.
Bangladesh has stepped up patrols on the border to try to stop the Rohingya from entering, but last week it said thousands had flooded into the country.
Those interviewed by AFP inside Bangladesh had horrifying stories of gang rape, torture and murder at the hands of Myanmar's security forces.
Analysis of satellite images by Human Rights Watch found hundreds of buildings in Rohingya villages have been razed.
Myanmar has denied allegations of abuse, saying the army is hunting "terrorists" behind raids on police posts last month.
Foreign journalists and independent investigators have been banned from accessing the area to probe the claims.
On Tuesday, the UN rights agency said Myanmar's treatment of the Rohingya could be tantamount to crimes against humanity, reiterating the findings of a June report.
The Office of the United Nations High Commissioner for Human Rights (OHCHR) also expressed alarm over reports of serious rights violations in Myanmar’s northern Rakhine state that cite allegations of extrajudicial killings, arbitrary arrests and sexual violence, and a renewed spike in hate speech – including on social media.
Tan said the UN was urging the Bangladesh government to allow the Rohingya safe haven.
"We are ready to support the government to provide effective humanitarian assistance for these individuals in need of international protection," she said. - IH