* In rare call, UN rights boss Zeid says may constitute genocide
* Human Rights Council condemns "likely crimes against humanity"
* Survivors have testified about "acts of extreme brutality"
* Myanmar envoy rejects resolution as politicised and partial (Adds Chinese foreign ministry, Amnesty International comments)
By Stephanie Nebehay
GENEVA, Dec 5 (Reuters) - Myanmar's security forces may be guilty of genocide against the Rohingya Muslim minority and more of them are fleeing despite a deal between Myanmar and Bangladesh to send them home, the top U.N. human rights official said on Tuesday.
The United Nations defines genocide as acts meant to destroy a national, ethnic, racial or religious group in whole or in part. Such a designation is rare under international law, but has been used in contexts including Bosnia, Sudan and an Islamic State campaign against the Yazidi communities in Iraq and Syria.
Zeid Ra'ad al-Hussein, U.N. High Commissioner for Human Rights, was addressing a special session of the Human Rights Council which later adopted a resolution condemning "the very likely commission of crimes against humanity" by security forces and others against Rohingya.
Myanmar's ambassador Htin Lynn said his government "dissociated" itself from the text and denounced what he called "politicisation and partiality".
Zeid, who has described the campaign in the past as a "textbook case of ethnic cleansing", said that none of the 626,000 Rohingya who have fled violence to Bangladesh since August should be repatriated to Myanmar unless there was robust monitoring on the ground. He described reports of "acts of appalling barbarity committed against the Rohingya, including deliberately burning people to death inside their homes, murders of children and adults; indiscriminate shooting of fleeing civilians; widespread rapes of women and girls, and the burning and destruction of houses, schools, markets and mosques".
"Can anyone - can anyone - rule out that elements of genocide may be present?" he told the 47-member state forum.
Shahriar Alam, Bangladesh's junior foreign affairs minister, told the session in Geneva that his country was hosting nearly one million "Myanmar nationals" following executions and rapes.
These crimes had been "perpetrated by Myanmar security forces and extremist Buddhist vigilantes", Alam said, calling for an end to what he called "xenophobic rhetoric..including from higher echelons of the government and the military".
Mainly Buddhist Myanmar denies the Muslim Rohingya are its citizens and considers them foreigners.
CHINA SEES "NEGATIVE IMPACT"
China's foreign ministry spokesman Geng Shuang on Wednesday told a regular news briefing that the resolution would not resolve or alleviate the situation.
"It could further complicate the issue and have a negative impact on Myanmar and Bangladesh implementing the repatriation agreement," he said.
China has supported Myanmar in the face of international criticism and has taken an increasingly active role in the issue, with foreign minister Wang Yi recently proposing a three step resolution during a visit to Myanmar.
But Nicholas Bequelin, East Asia director at Amnesty International, said in a statement that by voting against the resolution China has proved itself "woefully out of step" with world opinion and is serving to "preserve impunity for horrific crimes".
Marzuki Darusman, head of an independent international fact-finding mission on Myanmar, said by video from Malaysia that his team has interviewed Rohingya refugees, including children in the Bangladeshi port city of Cox's Bazar, who recounted "acts of extreme brutality" and "displayed signs of severe trauma".
Myanmar has not granted the investigators access to Rakhine, the northern state from which the Rohingya have fled, Darusman said. "We maintain hope that it will be granted early in 2018."
Pramila Patten, special envoy of the U.N. Secretary-General on sexual violence in conflict, who interviewed survivors in Bangladesh in November, said she had heard accounts of "rape, gang rape by multiple soldiers, forced public nudity and humiliation, and sexual slavery in military captivity".
Myanmar denies committing atrocities against the Rohingya. Its envoy Htin said: "People will say what they wanted to believe and sometimes they will say what they were told to say." (Reporting by Stephanie Nebehay in GENEVA, Additional reporting by Christian Shepherd and Michael Martina in BEIJING; Editing by Richard Balmforth & Simon Cameron-Moore)
Our Standards: The Thomson Reuters Trust Principles.