The United Nations has called for a probe into allegations that Myanmar troops have killed civilians and torched villages in northern Rakhine state, as fresh reports emerged of forced evictions in a security crackdown.
Aid agencies estimate more than 15,000 people have been displaced since the military took control of an area close to the Bangladesh border two weeks ago, a region which is home to the stateless Rohingya minority.
Myanmar's government says hundreds of Rohingya fighters led by a Taliban-trained jihadist were behind deadly raids on several police posts on October 9 that sparked a major security response.
Since then the military has stopped aid deliveries to tens of thousands of people in northern Rakhine and blocked access to rights groups and journalists.
Most of the people in the locked-down area are Rohingya -- a Muslim minority reviled by many in Myanmar as illegal immigrants from Bangladesh.
In a statement released late Monday, the UN urged Myanmar's government "to undertake proper and thorough investigations of alleged violations".
"Reports of homes and mosques being burnt down and persons of a certain profile being rounded up and shot are alarming and unacceptable," said the UN Special Rapporteur on summary executions Agnes Callamard.
"The authorities cannot justify simply shooting suspects down on the basis of the seriousness of the crime alone," she said, referring to the assaults on border guards that sparked the clampdown.
While details of military abuses are hard to verify, the UN said it has received "repeated allegations" of arbitrary arrests and extrajudicial killings "within the context of the security operations".
The violence has fanned fears of a repeat of the unrest that ravaged the state in 2012 and left more than 100 people dead.
Security forces have killed at least 31 people while defending themselves from attacks, according to a toll from state media and the military.
But Chris Lewa, from advocacy group the Arakan Project, says information from contacts in the area suggests the number killed is much higher.
Residents also say the crackdown, which has been led by the military but also includes border guard police forces, is intensifying.
Over the past two days, border officials have driven thousands of Rohingya from their homes in Kyikanpyin village, according to Maung Ni, a 32-year-old Rohingya shopkeeper.
"We are staying at another village," he told AFP. "We do not know what to do -- soldiers are still stationed inside the village."
Police sources, who asked not to be named, confirmed troops had searched the area for "terrorists" and some villagers had fled when they arrived.