Satellite data accessed by a rights body shows widespread fires burning in at least 10 areas in Myanmar’s Rakhine state, following a military crackdown on the country's Rohingya Muslim population.
Residents and activists have accused soldiers of shooting indiscriminately at unarmed Rohingya men, women and children and carrying out arson attacks.
However, authorities in Myanmar say close to 100 people have been killed since Friday when armed men, reportedly from the Arakan Rohingya Salvation Army (ARSA), launched a pre-dawn raid on police outposts in the restive region.
Myanmar authorities say Rohingya "extremist terrorists" have been setting the fires during fighting with government troops, while Rohingya have blamed soldiers who have been accused of carrying out extrajudicial killings.
A government spokesperson could not be immediately reached for comment.
"The Burmese government should grant access to independent monitors to determine the sources of fires and assess allegations of human rights violations," the Human Rights Watch (HRW) said in a statement on Tuesday.
The overall area in which burnings were found is 100 kilometres in length, approximately five times larger than the area where burnings by Burmese security forces occurred from October to November 2016, Human Rights Watch said.
In that period data from the group suggested some 1,500 buildings were destroyed.
The locations of the fires correlate with some witness statements and media reports describing blazes deliberately set, the group said.
"This new satellite data should cause concern and prompt action by donors and UN agencies to urge the Burmese government to reveal the extent of ongoing destruction in Rakhine State," Phil Robertson, HRW's deputy Asia director, said in a statement.
"Shuffling all the blame on insurgents doesn’t spare the Burmese [Myanmar] government from its international obligations to stop abuses and investigate alleged violations."
Antonio Guterres, the UN secretary-general, "is deeply concerned at the reports of civilians being killed," according to a statement from spokesman Stephane Dujarric.
Guterres called on Bangladesh to step up assistance to civilians escaping the violence, noting "many of those fleeing are women and children, some of whom are wounded".
More than 3,000 Rohingya have arrived in Bangladesh from Myanmar, where the Muslim ethnic minority faces persecution, in the past three days, the UN refugee agency UNHCR said on Monday.
The top UN human rights official called on authorities to ensure that the security forces refrain from using disproportionate force against Rohingya.
Zeid Ra'ad al-Hussein, UN High Commissioner for Human Rights, condemned coordinated attacks by rebels on security forces last Friday, but said that the political leadership had a duty to protect all civilians "without discrimination".
Bangladesh has said there are thousands more Rohingya Muslims massed on its border with Myanmar, where it has stepped up patrols and pushed back hundreds of civilians who have tried to enter.
|Aung San Suu Kyi: Turning her back on Rohingya?|
On Monday, Bangladesh detained and forcibly returned at least 90 Rohingya refugees back to Myanmar.
About 87,000 refugees entered Bangladesh in 2016 following the military crackdown.
The UN believes the army's response may amount to ethnic cleansing, allegations denied by the government of Aung San Suu Kyi and the army.
Meanwhile, Bangladesh has proposed joint military operations with Myanmar against Rohingya fighters in Rakhine state.
At the weekend, as violence in Rakhine worsened, Bangladesh's foreign minister summoned Myanmar's charge d'affaires in Dhaka to express "serious concern" at the possibility of a fresh refugee influx.
There are already almost 400,000 Rohingya refugees in Bangladesh in squalid camps near its border with Myanmar.
In a goodwill gesture, the Thai prime minister on Tuesday said his country was preparing to receive people fleeing fighting in Myanmar.
"Thailand's defence ministry and security are preparing to receive various displaced people," Prayuth Chan-ocha told reporters. "We will provide them with shelter like in the past ... and send them back when they are ready."
|Rohingya Muslims enter Bangladesh from a makeshift shelter near Cox's Bazar [Mohammad Ponir Hossain/Reuters]|