Myanmar's ruling junta ordered air strikes and troop reinforcements as it tried to recover lost outposts near the Chinese border from rebels, the military said.
The toppling of Aung San Suu Kyi's civilian government in a 2021 coup sparked a huge backlash and the military junta is now battling opponents across swaths of the country.
The Kachin Independence Army (KIA) attacked Myanmar military positions around Muse district in northern Shan state on Thursday and near the remote town of Laiza in Kachin state on Friday.
The military was forced to retreat on Friday afternoon and ordered air strikes, as well as artillery and troop reinforcements, the junta said in a statement shortly before midnight Friday.
The KIA said Saturday that the military had counter-attacked with air strikes and ground artillery.
It added that the junta had suffered some fatalities in the latest clashes this week but did not provide a death toll.
"We seized a lot of guns and other equipment from the military," KIA Colonel Naw Bu told AFP.
The KIA controls large parts of the Christian-majority Kachin state and has clashed with Myanmar's military for decades.
The region has seen intense fighting since the coup, and the junta accuses the KIA of training People's Defence Forces that have sprung up in resistance.
Muse lies on the path of a proposed $8.9 billion high-speed rail link from China's landlocked Yunnan province to Myanmar's west coast, a key part of Beijing's Belt and Road Initiative.
The junta has been accused of carrying out multiple bloody attacks on civilians as it struggles to crush resistance to its 2021 coup.
Nearly 30 people were killed and dozens were wounded this month after a military strike on a camp for displaced people near Laiza.
Amnesty International said the deadly attack on the camp was likely the result of the Myanmar military using a large unguided aerial-delivered bomb, while the junta blamed the explosion on a store of rebel bombs.
