The US State Department has said that it was "deeply, deeply troubled" by new reports of mass graves in Myanmar's Rakhine State, where the military has been accused of atrocities against minority Rohingya Muslims.
The Associated Press reported earlier it had confirmed the existence of more than five previously unreported mass graves in the Myanmar village of Gu Dar Pyin, through interviews of survivors in refugee camps in Bangladesh and through time-stamped cell phone videos.
"We are deeply, deeply troubled by those reports of mass graves," State Department spokeswoman Heather Nauert told a regular news briefing.
"We are watching this very carefully. We're mainly focused on helping to ensure the accountability for those responsible for human rights abuses and violations."
Ms Nauert said the reports highlighted the need for authorities in Myanmar to cooperate with an independent, credible investigation into allegations of atrocities in northern Rakhine state.
It comes as Myanmar's government told the UN Security Council that this month was "not the right time" for a visit by the UN body to see first-hand the Rohingya refugee crisis.
Kuwait's UN Ambassador, Mansour al-Otaibi, said Myanmar authorities were not opposed to such a visit, which could take place in March or April.
"They just think that this is not the right time for a visit," Mr Otaibi, who holds the council presidency for February, told reporters at UN headquarters.
The council has demanded that hundreds of thousands of Muslim Rohingya who were driven out of Rakhine state during an army crackdown be allowed to return.
The ambassador said Myanmar authorities were trying to organise a visit for diplomats based in the country, and had emphasised that "tensions are high in Rakhine state at the moment."
Nearly 700,000 Rohingya have crossed into Bangladesh and are living in refugee camps since August following the campaign that the United Nations has said was tantamount to ethnic cleansing.
Last month, the UN General Assembly adopted a resolution calling on UN Secretary-General Antonio Guterres to name a special envoy for Myanmar, but that appointment has yet to be made.
China, a supporter of Myanmar's former ruling junta, and Russia voted against the resolution.
