After the political leader of the M23 rebel group, Jean-Marie Runiga, was replaced Thursday, M23 forces loyal to military leader Sultani Makenga were attacked by those loyal to rebel commander Bosco Ntaganda in Bunagana, Democratic Republic of Congo, the BBC reported Friday.
Runiga is aligned with Ntaganda, who is wanted by the International Criminal Court on war crimes charges, the BBC added.
The U.N. High Commissioner for Refugees said about 4,500 people left Bunagana and crossed the border Thursday night.
"It started around midnight and we can still hear the bullets and bombs. Most of the town has fled," said Bunagana community leader Damien Batimaha.