A mayor in Central African Republic says members of a rebel group known as UPC have stormed his city with assault rifles and knives, killing at least six people.

Mayor Abel Matchipata told The Associated Press the armed rebels made their way into Bambari overnight and struck on Tuesday. Matchipata says they attacked his office and police and radio stations in retaliation for the deaths of three UPC members during a robbery outside the city Monday.

The rebel group is considered an offshoot of the mostly Muslim coalition known as Seleka, which overthrew Central African Republic's longtime president in 2013. Violence has since plagued the country.

Medecins Sans Frontieres representatives in the capital, Bangui, says more than 300 people sought refuge at Bambari hospital, where one civilian died.