GENEVA -- A report by the U.N. human rights office says attacks against Rohingya Muslims in Myanmar point to a strategy to instill "widespread fear and trauma" and prevent them from ever returning to their homes.

The report released Wednesday is based on 65 interviews conducted in mid-September with Rohingya, individually and in groups, as more the half a million people from the ethnic group fled into Bangladesh during a violent crackdown in Myanmar.

The attacks against Rohingya in Myanmar's northern Rakhine state by security forces and Buddhist mobs were "coordinated and systematic," with the intent of not only driving the population out of Myanmar but preventing them from returning, the report said.

Some of those interviewed said that before and during attacks, megaphones were used to announce: "You do not belong here - go to Bangladesh. If you do not leave, we will torch your houses and kill you."

According to the U.N. researchers, measures against the minority group began almost a month before the Aug. 25 attacks on police posts by Muslim militants that served as a pretext for what Myanmar's military called "clearance operations" in Rakhine.

"Information we have received indicates that days and up to a month before the 25th of August, that the Myanmar security forces imposed further restrictions on access to markets, medical clinics, schools and religious sites," Karin Friedrich, who was part of the U.N. mission to Bangladesh, said at a news conference. "Rohingya men aged 15 to 40 were reportedly arrested by the Myanmar police" and detained without any charges, she said.

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U.N. human rights chief Zeid Ra'ad al-Hussein said the Myanmar government's denial of rights, including citizenship, to the Rohingya appeared to be part of "a cynical ploy to forcibly transfer large numbers of people without possibility of return." He has also described the systematic attacks and widespread burning of villages as "textbook ethnic cleansing."

The report said efforts were made to "effectively erase signs of memorable landmarks" in Rohingya areas to make the landscape unrecognizable.

Myanmar's Buddhist majority denies that Rohingya Muslims are a separate ethnic group and regards them as illegal immigrants.