Myanmar's government admitted to launching airstrikes Wednesday against Kachin rebels in the country's northern region.
The statement from government leaders was broadcast on state television, and contradicted earlier reports that the government army was not carrying out such strikes, The Associated Press reported.
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UN Secretary-General Ban Ki-moon voiced concern over rising violence in the 20-month conflict between rebels and government forces.
"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," UN spokesman Martin Nesirky said in a statement obtained by Reuters.
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The strikes after weeks of heavy fighting at outposts about 10 miles outside the Kachin Independence Army headquarters on the Myanmar-China border, according to the Christian Science Monitor.
Government officials also claimed to have captured a hilltop post from which rebels launched attacks on government supply convoys.