The Myanmar military has said that dozens of soldiers were killed in clashes with Kokang ethnic rebels near the Chinese border.
According to the military, 47 government soldiers have been killed and dozens were left injured in clashes with the rebels.
The Kokang guerrilla forces "were found to be good at military manoeuvring with the use of scores of heavy weapons including anti-aircraft machine guns," a report on the state-run media The Global New Light of Myanmar said.
"While the state is making all-out efforts for reaching a nationwide ceasefire, the renegade groups of Kokang have ambushed the troops of the Tatmadaw," added the report.
Airstrikes are also thought to have been carried out.
The army did not specify the number of civilians or rebels who were killed during the violence, which is said to be one of the worst in several months.
The rebel groups, known as Myanmar National Democratic Alliance Army (MNDAA) has not commented on the fighting.
Without providing more information on the clashes, the military said 73 soldiers were wounded during the fighting which took place between Monday and Thursday this week.
The rise in violence is taking place when government authorities are forging ahead with a peace deal with the rebel groups.
China had also expressed concerns earlier this week, over the upsurge in the influx of people, who fled due to fighting, into the Yunnan province.