GENEVA — The United Nations expressed alarm on Friday about civilian deaths and other developing consequences from an escalating conflict between Myanmar’s military, which undertook a brutally violent military campaign against the Rohingya ethnic group, and an insurgent group in a western border region.

Ravina Shamdasani, a spokeswoman for the Office of the High Commissioner for Human Rights, said on Friday that the agency believed the violence in Rakhine State had also resulted in destroyed property, arbitrary arrests and abductions in civilian areas. She said that the fighting had displaced over 20,000 people.

Ms. Shamdasani said that at least seven civilians were killed on Wednesday, when two military helicopters bombed and strafed villagers who were tending cattle and working in rice fields. Eighteen more people were injured.

“The Myanmar military is again carrying out attacks against its own civilians,” Ms. Shamdasani said, adding that the attacks “may constitute war crimes.”