Myanmar's army accused rebels on Friday of attacking and killing "some" of its soldiers, the first skirmish acknowledged by the military in the wake of a rare ceasefire with ethnic armed groups.
The military announced last week it would suspend "all military movements" in the troubled northern and eastern regions for four months, a move observers say is unprecedented.
Halting a simmering decades-long civil war could be a way to coax ethnic armed groups into a fractious peace process, which has been marred by continuous fighting in restive border areas.
But the Tatmadaw, the military's Myanmar name, said their soldiers stationed in Shan state were attacked on Thursday by troops from the Shan State Army (SSA) -- also known as the Restoration Council of Shan State (RCSS).
"Some Tatmadaw men were killed and some injured in the attack were sent to the military hospital... for treatment," said a statement Friday from the Office of the Commander-in-Chief.
"The Tatmadaw will strongly stand by its...ceasefire declaration and respond in line with the law to the attacks of the SSA."
The army also hit out at local news outlets for publishing reports of skirmishes between the Tatmadaw and other armed groups, threatening "action in accordance with the law", said a statement posted Thursday by the military's information team.
A spokesman with RCSS's liaison office in Taunggyi, the capital of Shan State, denied the Myanmar army's account.
"Our local military commanders said it didn't happen among us," Lieutenant Colonel Sai Oo told AFP. "We have instructed our troops on the ground level already to avoid fighting."
Even with the army's declaration of a ceasefire, Myanmar's border regions are subjected to fighting between opposing armed groups.
The situation on the ground is "very complicated", said Brigadier General Tarr Phone Kyaw, a spokesman for the Taaung National Liberation Army (TNLA) -- one of the larger ethnic armed groups battling the military in the northeast.
While the TNLA is still battling the RCSS, Tarr Phone Kyaw said they are honouring the ceasefire with Myanmar government troops and there has been "no offensive" against them.
"We have been instructed to stay in our own area," he told AFP.
Conflicts have been festering in border areas since independence from Britain 70 years ago, with various armed groups fighting for autonomy, identity, resources and territory.
The peace process has been defacto leader Aung San Suu Kyi's stated priority since her party swept to power in landmark elections in 2015, as the country opened up following half a century of military rule.
But she has had no say over security policy, with the military retaining key government posts in a delicate power-sharing arrangement.