U.N. Secretary-General Ban Ki-moon expressed concern about reports that Myanmar's air force targeted rebel positions in northern Kachin. Myanmar authorities are called on to ensure the civilian population in the area is shielded from conflict, he said in a statement issued by his spokesman's office.
"The ongoing hostilities have already caused large-scale displacement of civilians, who continue to be in need of humanitarian assistance," Ban's statement read. "It is vital that timely access be provided for the delivery of aid to vulnerable communities."
The BBC this week broadcast a video taken by the humanitarian agency Free Burma Rangers that shows what appears to be a military air strike on Kachin rebels. A government spokesman told Voice of America later that jets were used to regain territory held by the rebel Kachin Independence Organization.
Fighting in Kachin erupted in 2011, ending a 17-year truce.
Myanmar, a country known formerly as Burma, has received international praise for a series of political reforms that began with general elections in 2010, though security and human concerns continue to tarnish the government's reputation.