The main United Nations human rights agency has expressed concern about an upsurge in fighting between Myanmar's army and guerrillas of the Rakhine minority's Arakan Army, especially attacks on civilians by both sides.

A spokeswoman for the U.N. High Commissioner for Human Rights said Friday in Geneva that the agency had "credible reports of the killing of civilians, burning of houses, arbitrary arrests, abductions, indiscriminate fire in civilian areas, and damage to cultural property."

The spokeswoman, Ravina Shamdasani, said recent fighting in Rakhine state has led to the displacement of more than 20,000 civilians. Rakhine is best known as the site of a brutal counterinsurgency campaign by the military against the Muslim Rohingya minority which caused more than 700,000 to flee to neighboring Bangladesh.