US Secretary of State Rex Tillerson has said that the actions of the Myanmar's military against the minority Muslim Rohingya population constitutes ethnic cleansing.

He said the Rohingya had suffered "horrendous atrocities" and as the US is consqeuently considering targeted sanctions against those responsible.

"After a careful and thorough analysis of available facts, it is clear that the situation in northern Rakhine state constitutes ethnic cleansing against the Rohingya," Mr Tillerson said in a statement.

"These abuses by some among the Burmese military, security forces, and local vigilantes have caused tremendous suffering and forced hundreds of thousands of men, women, and children to flee their homes in Burma to seek refuge in Bangladesh," he said.

"Those responsible for these atrocities must be held accountable," he added.

In September, UN human rights chief Zeid Raad Al Hussein also accused Myanmar of ethnic cleansing.

Tillerson’s statement is are a divergence from his stance earlier this week, when he refused to use the term “ethnic cleansing” when describing the Myanmar military's actions in their western Rakhine State, saying instead he was "very concerned" about the reports.

"What we know occurred in Rakhine state ... has a number of characteristics of crimes against humanity," he said on November 15, after an official visit to Myanmar.

"Whether it meets all the criteria of ethnic cleansing we continue to determine ourselves."

This comes less than a week before Pope Francis is due to land in Myanmar for a week-long visit to the region, including a trip to Bangladesh.

Since August 25 an estimated 615,000 Rohingya have fled across the border into neighboring Bangladesh, bringing with them horrific stories of executions, widespread arson and systematic rape.

Meanwhile, Myanmar has repeatedly denied claims it is deliberately attacking Rohingya civilians, and claim that they are fighting against a terrorist insurgency in the province.