YANGON (AFP) - Myanmar has moved hundreds of troops into northern Rakhine state as it ramps up counterinsurgency efforts there, officers told AFP on Saturday (Aug 12), after the UN voiced alarm over reports of a military build-up in the region.

Rakhine has been gripped by violence since October last year when militants attacked police posts, sparking a bloody military crackdown that the UN believes may amount to ethnic cleansing of the Muslim minority Rohingya.

More than 70,000 Rohingya villagers fled across the border to Bangladesh, carrying with them stories of systematic rape, murder and arson at the hands of soldiers.

The major part of the military campaign ended several months ago, but fear continues to stalk the region amid sporadic bouts of violence.

Officers said on Saturday that the government had deployed a fresh batch of troops after a recent spate of murders.

They said soldiers have been sent to a mountainous area where a band of militants is actively training.

"Many battalions with hundreds of soldiers from central Myanmar were deployed to the Mayu moutain range," a military officer told AFP, requesting anonymity.

A senior border guard said the deployment was ordered to protect other ethnic groups in the remote area.

The government has accused insurgents of murdering and abducting dozens of villagers and perceived collaborators with the state.

"Muslim militants are training in the forest... They have killed those who are cooperating with authorities," the border guard told AFP.

State media also reported that the government had imposed new curfews, to be set "in necessary areas" as the army beefs up its "clearance operations".

A Rohingya villager told AFP that his community feared a repeat of last year's crackdown.

"Some Muslim villages in Rathidaung dare not to go outside," said Hasumyar, who only gave his first name and lives in a township that has been placed under curfew.

The insurgents, known as the Arakan Rohingya Salvation Army, were little known until they claimed the October raids on police posts that left nine dead.

The group says it is fighting to advance the rights of the Rohingya and has denied killing civilians, in statements issued through an unverified Twitter account.

Reports of an army battalion being flown into Rakhine to boost security were met with criticism on Friday by UN special rapporteur Yanghee Lee, who warned the development was "a cause for major concern".

The UN has accused the military of committing grave abuses against the Rohingya during its counterinsurgency campaign.

But Myanmar has dismissed the allegations and vowed to block a UN probe into the violence.

Buddhist-majority Myanmar has long faced criticism for its treatment of the more than one million Rohingya, who are denied citizenship and struggle to access basic services.

The minority group are widely reviled as illegal migrants from Bangladesh, despite having lived in the area for generations.