WASHINGTON - The US has called for the restoration of access for humanitarian organisations and the media in Myanmar's Rakhine state, and the calming of tensions and violence that has driven well over 200,000 Rohingya Muslims across the border into Bangladesh since Aug 25.

"We condemn attacks of a variety of nature, attacks on security forces, attacks on civilians, attacks by civilians, and we are very concerned about the sustained allegations of abuses being committed that is resulting in the displacement of many people," Deputy Assistant Secretary of the State Department's Bureau of East Asian and Pacific Affairs Patrick Murphy told journalists in Washington.

Acknowledging the particularly complex nature of the issue in northern Rakhine state, he said: "We are urging all parties to take steps to calm tensions, and authorities and partners of the Burmese authorities to continue to address the underlying challenges which are behind the most recent eruption of violence."

"Primarily this is an ethnic issue, the Rohingya have been treated separately, they… have been devoid of basic rights for many many years," he said.

"In addition to the challenges being long-standing, they are very complex and there are some new troubling dimensions. On Aug 25, the attacks on security forces were quite substantial, quite coordinated," he added.

"This is relatively new and there were casualties. That creates a lot of concern, a lot of fear and a requirement of security forces to respond. Obviously, the response needs to be in accordance with the rule of law and respect for human rights and in ways that protect local populations," Mr Murphy said.

"With the movement of a large number of people both across the border and internally it's quite clear they are fearful of their security" he added.

The US in talks with the Myanmar government was identifying "very willing partners within the government who understand the situation," Mr Murphy said.

The US' immediate focus was "instant and very urgent re-access for humanitarian assistance and the media but also efforts to calm tensions, that security forces act responsibly, and indeed that civilians act responsibly."

"Another complex new dimension is local militia among local populations who are attacking civilians, that adds to this cauldron and hotspot nature of northern Rakhine state," he noted.