More than 2,600 houses have been burned down in Rohingya-majority areas of Myanmar's northwest in the last week, the government said on Saturday, in one of the deadliest bouts of violence involving the Muslim minority in decades.

About 58,600 Rohingya have fled into neighbouring Bangladesh from Myanmar, according to U.N. refugee agency UNHCR, as aid workers there struggle to cope.

Myanmar officials blamed the Arakan Rohingya Salvation Army (ARSA) for the burning of the homes. The group claimed responsibility for coordinated attacks on security posts last week that prompted clashes and a large army counter-offensive.

But Rohingya fleeing to Bangladesh say a campaign of arson and killings by the Myanmar army is aimed at trying to force them out.

The treatment of Buddhist-majority Myanmar's roughly 1.1 million Rohingya is the biggest challenge facing leader Aung San Suu Kyi, accused by Western critics of not speaking out for a minority that has long complained of persecution.

The clashes and army crackdown have killed nearly 400 people and more than 11,700 "ethnic residents" have been evacuated from the area, the government said, referring to the non-Muslim population of northern Rakhine.

It marks a dramatic escalation of a conflict that has simmered since October, when similar but much smaller Rohingya attacks on security posts prompted a brutal military response dogged by allegations of rights abuses.

"A total of 2,625 houses from Kotankauk, Myinlut and Kyikanpyin villages and two wards in Maungtaw were burned down by the ARSA extremist terrorists," the state-run Global New Light of Myanmar said on Saturday. The group has been declared a terrorist organisation by Myanmar government.

But New York-based Human Rights Watch, which analyzed satellite imagery and accounts from Rohingya fleeing to Bangladesh, said the Myanmar security forces deliberately set the fires."New satellite imagery shows the total destruction of a Muslim village, and prompts serious concerns that the level of devastation in northern Rakhine state may be far worse than originally thought," said the group's deputy Asia director, Phil Robertson.

Near the Naf river separating Myanmar and Bangladesh on Saturday, new arrivals in Bangladesh carrying their belongings in sacks were setting up crude shelters or trying to squeeze into available shelters or homes of local residents.

"The existing camps are near full capacity and numbers are swelling fast. In the coming days there needs to be more space," said UNHCR regional spokeswoman Vivian Tan, adding that more refugees were expected.

The Rohingya are denied citizenship in Myanmar and regarded as illegal immigrants, despite claiming roots that date back centuries. Bangladesh is also growing increasingly hostile to Rohingya, more than 400,000 of whom live in the poor South Asian country after fleeing Myanmar since the early 1990s.

Jalal Ahmed, 60, who arrived in Bangladesh on Friday with a group of about 3,000 after walking from Kyikanpyin for almost a week, said he believed the Rohingya were being pushed out of Myanmar.

"The military came with 200 people to the village and started fires... All the houses in my village are already destroyed. If we go back there and the army sees us, they will shoot," he said.

Reuters could not independently verify these accounts as access for independent journalists to northern Rakhine has been restricted since security forces locked down the area.