Sydney | More than 500 people are feared dead after reports that two boats carrying members of Myanmar's persecuted Rohingya minority have capsized in the Bay of Bengal, officials said Thursday.

According to preliminary information, the two boats left Myanmar's western state of Rakhine in late June carrying mostly Rohingya passengers, including some who had travelled from refugee camps across the border in Bangladesh, according to a statement from the International Organisation for Migration and the United Nations High Commissioner for Refugees.

One boat, believed to have been carrying around 250 people, lost contact shortly after departure. A second boat, reportedly carrying 280 people, is believed to have sunk off Myanmar's Ayeyarwady coast on July 8.

"While the incidents and casualty figures have yet to be officially confirmed, UNHCR and IOM are gravely concerned by the potentially devastating loss of life," the agencies said.