KAMPALA, Uganda -- A spokeswoman for the U.N. refugee agency in Uganda says more than 4,000 Congolese refugees crossed into Uganda Thursday night to escape renewed violence in eastern Congo.

Lucy Beck of UNHCR said Friday that the refugees were fleeing battles between armed factions of M23, a rebel group that opposes the government of Congolese President Joseph Kabila. Beck said the agency is bracing itself for a greater influx in coming weeks, although there were no reported arrivals Friday.

The refugees were stranded at the Bunagana border post and had refused to relocate to transit centres, apparently to keep monitoring for signs of peace, she said.

M23 is said to be undergoing a power struggle, with the military wing reportedly taking over authority previously held by a cleric named Jean- Marie Runiga.