UN Secretary-General Ban Ki-moon has voiced concern at reports of air strikes in Myanmar's Kachin State, where a 20-month conflict between government troops and rebels has been escalating.
"(Ban) has taken serious note of the most recent reports indicating air strikes against targets in Kachin State," UN spokesman Martin Nesirky said in a statement.
"While details of these reports are still emerging and being closely followed, the Secretary-General calls upon the Myanmar authorities to desist from any action that could endanger the lives of civilians living in the area or further intensify the conflict in the region," he said.
Myanmar, also known as Burma, has introduced social and economic reforms since a quasi-civilian government took power in 2011 after nearly half a century of military rule.
The changes have attracted large numbers of foreign investors and prompted the United States and European Union to ease longstanding sanctions to encourage further reform.
But ethnic conflicts continue across the Southeast Asian nation, including in Kachin State.
"The ongoing hostilities have already caused large-scale displacement of civilians who continue to be in need of humanitarian assistance," Nesirky said. "It is vital that timely access be provided for the delivery of aid to vulnerable communities."