Myanmar's junta appears to be "trying to destroy a country it cannot control", the UN special rapporteur to the country warned on Thursday.
Clashes between an alliance of ethnic minority armed groups and the military have shredded a Beijing-brokered truce in January.
The ceasefire had briefly halted widespread fighting in the northern part of the Southeast Asian nation since a military coup ended democratic rule in 2021.
"The junta is on its heels, it's losing troops, it's losing military facilities, it is literally losing ground," UN special rapporteur Tom Andrews said during a briefing to the national security body of neighbouring Thailand.
"It almost appears as if the Junta is trying to destroy a country that it cannot control."
The military's response to its losses has been to attack civilians, he said, adding there had been a substantial increase in the number of attacks on schools, hospitals and monasteries in the last six months.
"The stakes are very very high."
Ethnic minority fighters seized a town from the military along a key trade highway to China's Yunnan province earlier this week after days of clashes.
The northern Shan state has been rocked by fighting since late last month, when an alliance of ethnic armed groups renewed an offensive against the military.
The clashes have eroded a Beijing-brokered truce that halted an offensive by the alliance of the Arakan Army (AA), the Myanmar National Democratic Alliance Army (MNDAA) and the Ta'ang National Liberation Army (TNLA).
