More than 22,000 people from mainly Muslim communities have been forced to flee their homes in western Myanmar, the UN said Sunday, after a fresh wave of violence and arson that left dozens dead.

Whole neighbourhoods were razed in last week's clashes between Buddhists and Muslims in Rakhine state, which has cast a shadow over the country's reforms and put further strain on relief efforts in the region.

Some 75,000 people are already crammed into overcrowded camps following clashes in June.

The United Nations chief in Yangon, Ashok Nigam, said government estimates provided early Sunday were that 22,587 people had been displaced and 4,665 houses set ablaze in the latest bloodshed.

"These are people whose houses have been burnt, they are still in the same locality," he told AFP, indicating that thousands more who had fled in boats towards the state capital Sittwe may not be included in that estimate.

"It is mainly the Muslims who have been displaced," he said, adding that 21,700 of those made homeless were Muslims.

The latest fighting has killed more than 80 people, according to a government official, bringing the total death toll since June to above 170.

In Minbya, one of around eight townships hit by the fighting, a senior police official told AFP that more than 4,000 people, mainly Muslims, had been made homeless after hundreds of properties in six villages were torched.

"Some victims are staying at their relatives' houses, some are in temporary relief camps, they are staying near those burnt areas," he said, adding that a heightened security presence had prevented further clashes.

"They are staying between Muslims and Rakhine people," he said.

Festering animosity between Buddhists and Muslims have continued to simmer in Rakhine since June. It is seen as presenting a serious challenge to Myanmar's new quasi-civilian government, which has ushered in a series of reforms since replacing a feared junta last year.

Zaw Htay, an official from the office of President Thein Sein, said there had been no new clashes since Saturday. Under a state of emergency imposed after the June unrest, security had been tightened across Rakhine state but the new violence had "occurred in unexpected areas", he said.

He said police were hunting "manipulators" behind the unrest.

"We are giving this issue particular attention for the sake of national security," he told AFP.

Authorities are trying to provide emergency relief to those affected as a first priority, followed by giving them shelter and health care.

"Generally speaking, the situation is under control. The primary concern now is to make sure the problem of the refugees does not increase," Zaw Htay said.

Nigam, who has just returned from a visit to affected areas, said the UN was concerned both about the potential for a further spread of violence and the fact that it would be "more challenging" to reach the displaced in remote areas.

He said the UN had already started mobilising to take food and shelter to displaced communities, "but we will quickly need more resources".

Around 6,000 people had arrived in Sittwe seeking shelter in camps on the outskirts of the city that are already packed with Muslim minority Rohingya following June's unrest, a state spokesman said Saturday.

Overstretched local authorities said they were looking to relocate them to another area.

Human Rights Watch on Saturday released satellite images showing "extensive destruction of homes and other property in a predominantly Rohingya Muslim area" of Kyaukpyu.

The images show a stark contrast between the coastal area as seen in March this year, packed with hundreds of dwellings and fringed with boats. In the aftermath of the latest violence, virtually all structures appear to have been wiped from the landscape.

Myanmar's 800,000 Rohingya are seen as illegal immigrants from neighbouring Bangladesh by the government and many Burmese -- who call them "Bengalis". They face discrimination that activists say has led to a deepening alienation from Buddhists.

The stateless group, speaking a Bengali dialect similar to one in Bangladesh, have long been considered by the United Nations as one of the most persecuted minorities on the planet.

Bangladesh said Sunday it had mobilised extra patrols along its river border with Myanmar but no boats carrying Rohingya had tried to cross.

Other Muslims in Rakhine state have also been swept up in the latest violence, activists said.

"It is not just the Rohingya who are targeted, it is Muslims in general, particularly Kamans, who are a recognised minority and have the citizenship," said Chris Lewa, head of the Arakan Project which campaigns for Rohingya rights.

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