YANGON, Jan 2 (Reuters) - Myanmar has promised to take action against policemen who beat Muslims after footage of villagers being treated violently appeared online amid tension over a government crackdown aimed at rooting out suspected insurgents.

Troops have poured into Rakhine State on Myanmar’s northwestern border with Bangladesh since gunmen attacked border posts on Oct. 9, killing nine officers.

The Myanmar army sweep has sent some 34,000 members of the Rohingya Muslim minority fleeing into neighboring Bangladesh, the United Nations says.

Residents and rights groups accuse security forces of abuses during the operation including summary executions and rape, which the government of Aung San Suu Kyi denies.

In footage shared widely on social media and aired by Myanmar broadcasters, several policemen appeared to beat and kick two villagers during an operation in which dozens of Rohingya Muslims were told to line up for questioning.

The video offers a rare glimpse into the region that has been cut off to aid workers and other outsiders since October.

Suu Kyi’s office confirmed the authenticity of the footage, which it said was shot by a member of the police during a clearance operation on Nov. 5 in northern Rakhine State.

“Action will be taken against police who allegedly beat villagers,” the office said in a statement issued late on Sunday.

Police were acting on a tip-off that gunmen who attacked police two days earlier were being sheltered in the village, called Kotankauk, the office said.

The office identified four policemen by name, including the leader of the operation and one it said could be seen beating villagers in the video.

“Further investigations are being carried out to expose other police officers who beat the villagers,” it said.

A senior police officer in the capital of Naypyitaw told Reuters authorities detained four policemen on Monday on suspicion they were involved in the beating. The officer declined to be identified as he is not authorized to speak to media.

The violence in Rakhine State has renewed international criticism that Nobel Peace Prize winner Suu Kyi has done too little to help members of the Muslim minority, who are denied citizenship in predominantly Buddhist Myanmar.

The government has blamed militants with links to Islamists overseas for the Oct. 9 attacks. State media has reported at least 86 deaths in the security force operation that followed.