Myanmar's four-month military crackdown on Rohingya Muslims has likely killed hundreds of people, the UN said Friday in a report detailing horrific abuses allegedly committed against civilians in Rakhine state.

“The 'area clearance operations' have likely resulted in several hundred deaths,” said the report from the United Nations human rights office, referring to the military crackdown launched on October 10.

The report based on interviews with 204 Rohingya refugees who have fled to Bangladesh said it was “very likely” that crimes against humanity had been committed in Myanmar, echoing similar accusations made by UN officials.

Victims recounted gruesome violations allegedly perpetrated by members of Myanmar's security services or civilian fighters working alongside the military and police.

“An eight-month-old baby was reportedly killed while his mother was gang-raped by five security officers,” the rights office said in a press release, citing witness accounts.

The UN also said it had reports of three children aged six or younger being “slaughtered with knives”.

“What kind of hatred could make a man stab a baby crying out for his mother's milk,” UN rights chief Zeid bin Ra'ad Zeid al-Hussein said in the statement.

“What kind of 'clearance operation' is this? What national security goals could possibly be served by this?”, he added.

A full 47 percent of those interviewed by the UN said they had a family member who had been killed in the operation, while 43 percent reported being raped.

The Rohingya are loathed by many among Myanmar's Buddhist majority.

Yangon refuses to recognise the Rohingya as one of the country's ethnic minorities, instead describing them as Bengalis -- or illegal immigrants from neighbouring Bangladesh -- even though many have lived in Myanmar for generations.

The military crackdown in Rakhine, home to more than one million Rohingya, was triggered by a series of October 9 attacks on border guard posts.

Yangon's own probe into the unrest denied that the security forces had carried out a genocidal campaign against the Rohingya.

Myanmar's government, led by Nobel laureate Aung San Suu Kyi, has said the allegations are invented and has resisted mounting international pressure to protect the minority.

But Zeid, who has previously urged Yangon to act, hit back again on Friday demanding that impunity for such serious crimes had to stop.

“The Government of Myanmar must immediately halt these grave human rights violations against its own people, instead of continuing to deny they have occurred,” he said.