More than 26,000 people have been displaced in Myanmar's western Rakhine state this week, the United Nations said on Friday.
Meanwhile, a leading opposition group and residents in a village in the western Chin state said 11 civilians were killed in an air strike.
Myanmar's junta has been fighting on multiple fronts against rebel groups in various states.
What did the UN say about displaced persons in Rakhine?
Militants of the Arakan Army (AA) launched attacks on security forces in Rakhine and neighboring Chin state on Monday, which ended a cease-fire and opened another front in the conflict in Myanmar.
The AA militant group has for years demanded more autonomy for the ethnic Rakhine population. The ethnic group form the majority of the population in Rakhine, which also traditionally houses the stateless Rohingya people.
The United Nations Office for the Coordination of Humanitarian Affairs (UNOCHA) said the "clashes have resulted in the displacement" of 26,175 people.
UNOCHA said at least 11 people had been killed in military shelling of AA positions since Monday.
The AFP news agency cited local residents as saying that junta troops shelled the Chin town of Paktauw after AA militants briefly seized the police station.
UNOCHA said 19,000 people had been displaced from Pauktaw.
The UN agency said that "virtually all" roads and waterways connecting townships in Rakhine had been blocked and that most humanitarian activities had been suspended.
It said that over 100 people had reportedly been detained by authorities since the start of the clashes.
Strike kills 11 civilians in Chin state
An attack on Wednesday on the village of Vuilu in the southern Matupi township in Chin state killed at least 11 civilians, according to an opposition group and residents cited by the Associated Press.
The junta has not announced any attacks at the location.
Ngai Tam Maung, an official in the opposition National Unity Government, told the Associated Press that two military jets dropped bombs on buildings in Vuilu.
He said a church, two school buildings and 18 houses in the village were damaged. The village has around eight houses.