* Factions fight near Ugandan border
* Insurgent split complicates peace efforts
* Renegade general wanted by International Criminal Court
By Jonny Hogg
KINSHASA, March 1 (Reuters) - Thousands of Congolese civilians fled to neighbouring Uganda on Friday to escape clashes between rival rebel factions, one of them led by Bosco Ntaganda, a renegade general wanted on war-crimes charges, witnesses said.
Fighting in eastern Congo spilled into a second day after the M23 rebel group's military command sacked the group's political leader on Thursday for his links with Ntaganda, prompting fighters to turn their weapons on each other.
The violence risks complicating attempts to find a lasting peace in the region and exacerbating a dire humanitarian crisis. Hundreds of thousands have been driven out of their homes by conflict in recent years.
Around 6,000 residents of the border town of Bunagana began crossing into Uganda on Thursday and Friday as fighting edged closer, residents said. Light and heavy weapons fire continued through the night in hills around the town, as Ntaganda's men attacked positions held by M23's military commander Sultani Makenga.
"It started at around midnight and we can still hear the bullets and bombs. It's Makenga's men who control the town ... Most of the town has fled. I'm at home but my family has already left," said Damien Batimaha, a local community leader.
Colonel Vianney Kazarama, a spokesman for M23, confirmed the fighting. "They (Ntaganda's men) organised an attack against General Makenga's headquarters at Chanzu - 11 km (7 miles) from Bunagana. He repulsed them throughout the night and they have fled, leaving lots of bodies and wounded behind," he said.
Other towns in the area - which has been under M23 control since last year - were pillaged by local militias and rebel groups as M23 soldiers pulled out, according to local sources.
"Rutshuru is in the hands of FDLR, they've been pillaging the shops," a businessman from the town said, in reference to the Rwandan Hutu extremist group active in eastern Congo for nearly two decades and blamed for committing some of the worst atrocities against civilians. He asked not to be named.
The power struggle within M23 ranks will further damage efforts to revive peace talks hosted by Uganda and may spur the Kinshasa government to push for a military solution to the recurring rebellions in the east.
Ntaganda - whose defection from the army in March last year helped spark the insurgency - is wanted by the International Criminal Court for alleged massacres during a previous rebellion.
His exact whereabouts remained unclear but on Thursday the bulk of his troops were pushed out of the town of Kibumba, 25 km north of Goma. Local sources said they were currently in the thick forests of the Virunga National Park, which border on Ntaganda's political heartland of Masisi.
Separately, the UN said that around 3,000 people had crowded around their base in the town of Kitchanga, after clashes on Thursday between the Congolese army and fighters from a formerly pro-government militia.
"The situation is very bad ... It's tense right now but we are patrolling," said Alexandre Essome, spokesman for the UN's peacekeeping operation in Goma.
Eastern Congo has suffered nearly two decades of violence, with civilians regularly caught in the crossfire as a multitude of rebel groups and the country's poorly trained and corrupt army battle for control of land and mineral resources. (Editing by Richard Valdmanis and Andrew Roche)