Elements of the Allied Democratic Forces attacked a town in eastern DRC. The International Committee of the Red Cross said more than 18,000 people fled into neighboring Uganda to escape the rebels since attacks began Thursday, the BBC reports.
Regional ICRC chief Franz Rauchenstein said in June the situation in eastern DRC was "very worrying."
ADF is a Uganda rebel movement based in eastern DRC. Ugandan military spokesman Lt. Col. Paddy Ankunda told the United Nations' Integrated Regional Information Networks the rebel group was recruiting fighters from eastern DRC.
"The threat is real," he said Thursday. "We are alert and very prepared to deal with any attack on our side of the border."
The U.N. news agency reports the rebel force ousted the DRC military in North Kivu province, near the Ugandan border, before pulling back during Thursday fighting.
Members of the March 23 Movement rebelled against the DRC government last year. The movement is suspected of committing war crimes during its siege on North Kivu province in the east of the country.
M23 forces seized control over the provincial capital briefly during heavy fighting last year.