* Groups say need funding to help 1.2 million people
* Half a million people need food assistance
* Rights group reports massacre in August (Updates with comment from Amnesty International)
By Rahul Bhatia
COX'S BAZAR, Bangladesh, Oct 4 (Reuters) - Humanitarian organisations helping Rohingya Muslim refugees in Bangladesh said on Wednesday they need $434 million over the next six months to help up to 1.2 million people, most of them children, in dire need of life-saving assistance.
There are an estimated 809,000 Rohingya sheltering in Bangladesh after fleeing violence and persecution in Myanmar, more than half a million of whom have arrived since Aug. 25 to join 300,000 Rohingya who are already there.
"Unless we support the efforts of the Bangladesh government to provide immediate aid to the half million people who have arrived over the past month, many of the most vulnerable – women, children and the elderly – will die," said William Lacy Swing, director general of the International Organization for Migration, which is coordinating the aid effort.
"They will be the victims of neglect."
About 509,000 Rohingya have arrived in Bangladesh since attacks by Rohingya militants in August triggered a sweeping Myanmar military offensive that the United Nations has branded ethnic cleansing.
Myanmar rejects accusations of ethnic cleansing. It says its forces are fighting insurgents of the Arakan Rohingya Salvation Army (ARSA) who claimed responsibility for attacks on about 30 police posts and an army camp on Aug. 25.
The insurgents were also behind similar but smaller attacks in October last year that led to a brutal Myanmar army response triggering the flight of 87,000 Rohingya to Bangladesh.
The agencies' plan for help over the next six months factors in the possibility of another 91,000 refugees arriving, as the influx continues, Robert Watkins, U.N. resident coordinator in Bangladesh, said in a statement.
"The plan targets 1.2 million people, including all Rohingya refugees, and 300,000 Bangladeshi host communities over the next six months," Watkins said..
Half a million people need food while 100,000 emergency shelters are required. More than half the refugees are children, while 24,000 pregnant women need maternity care, the agencies said.
U.N. appeals for funds to help with humanitarian crises are generally significantly under-funded.
GROUP REPORTS MASSACRE
The Rohingya are regarded as illegal immigrants in Buddhist-majority Myanmar and most are stateless.
Myanmar leader Aung San Suu Kyi has faced scathing criticism for not doing more to stop the violence, although she has no power over the security forces under a military-drafted constitution.
She has condemned rights abuses and said Myanmar was ready to start a process agreed with Bangladesh in 1993 under which anyone verified as a refugee would be accepted back.
But many Rohingya are pessimistic about their chances of going home, partly because few have official papers confirming their residency.
Most are also wary about returning without an assurance of citizenship, which they fear could leave them vulnerable to the persecution and discrimination they have endured for years.
The rights group Amnesty International said the international community had to ensure that no refugees are forced back to Myanmar as long as they remain at risk of serious rights violations.
The U.N. refugee agency says any repatriation has to be voluntary.
Human Rights Watch said it had found evidence that the Myanmar military had summarily executed dozens of Rohingya in a village called Maung Nu in Rakhine state, on Aug. 27, two days after the insurgent attacks triggered the violence.
The rights group said it had spoken to 14 survivors and witnesses who were now refugees in Bangladesh. They described how soldiers entered a compound where people had gathered in fear of military retaliation.
"They took several dozen Rohingya men and boys into the courtyard and then shot or stabbed them to death. Others were killed as they tried to flee," said the rights group, which has accused Myanmar of crimes against humanity.
Spokesmen for the government, the military and police did not answer their telephones and were not available for comment. Wednesday is a holiday in Myanmar.
Reuters was not able to independently verify the report.
The U.N. committees for women's and children's rights called on Myanmar to immediately stop violence in Rakhine, saying violations "being committed at the behest of the military and other security forces" may amount to crimes against humanity. (Addtional reporting by Shoon Naing in YANGON, Tom Miles in GENEVA, Michelle Nichols in NEW YORK; Writing by Robert Birsel; Editing by Paul Tait and Nick Macfie)
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