Burma's military has admitted launching air strikes against ethnic Kachin rebels in the north and said it captured a hilltop post from where the insurgents had attacked government supply convoys.
The statement broadcast on state television contradicted government claims two days earlier that the military was not carrying out offensive air attacks on the Kachin, raising questions about how much control the elected government of reformist president Thein Sein has over the army.
The United States said on Wednesday the use of air power in Kachin state was "extremely troubling". In Washington, State Department spokeswoman Victoria Nuland urged the government and the Kachin rebel group to cease their conflict and begin a real dialogue for peace.
United Nations secretary general Ban Ki-moon called on Burma's 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 called on the government and rebels to work towards political reconciliation.
Burma state television, quoting the Defence Ministry, said the military occupied a Kachin Independence Army hilltop post on Sunday during a mopping-up operation of the area where attacks had been launched against supply convoys.
The government has been seeking to supply a base at Lajayang very close to KIA headquarters at Laiza, the rebel group's last major outpost.
The government delivered an ultimatum to the Kachin to clear a road by Christmas Day so it could supply its base. The Kachin rejected the ultimatum for fear of a government attack on its own outpost.
KIA spokesman La Nan said on Monday that the supplies being sent to government troops included ammunition as well as rice. "We will obstruct any army convoy that carries arms and ammunition that will be used against us," he said. "This is the nature of war."
Each side blames the other for intensified fighting that began a little over a week ago.
The Kachin said on Monday it was being attacked by helicopter gunships and fighter jets, but President's Office director Major Zaw Htay said the aircraft were being used mainly to supply government units whose access to supplies by road had been cut off by the Kachin guerrillas.