The Democratic Republic of Congo's newest rebel movement is threatening to attack the army in a major eastern town that the insurgents had handed over to police and United Nations peacekeepers. The M23 rebels, in a statement, have called for the soldiers to leave Rutshuru and neighbouring Kiwanja or "be held responsible for all related consequences". Rebels had taken Rutshuru last Sunday as soldiers retreated before their advance and UN peacekeepers chose not to fire from armoured personnel carriers. The rebels vacated the town voluntarily on Monday, warning the army not to return. They said they were retreating to the Congo-Uganda border crossing of Bunagana to await word on the government's willingness to negotiate. DR Congo's government has said it will negotiate only with Rwanda, which is accused of supporting the rebels. Rwanda denies this but agreed this week at a meeting on the sidelines of an African Union summit to the creation of "a neutral international force to eradicate" rebels and militias in eastern Congo and to patrol the Congo-Rwanda border. DR Congo has the world's largest peacekeeping force of about 20,000 troops and police that cost nearly $US1.5 billion last year. It was unclear how another force could succeed where the UN has failed in helping bring peace to eastern Congo, where more than a dozen local militias and foreign rebel groups run amok. On Thursday, the UN confirmed it had deployed helicopter gunships to bombard several M23 positions. DR Congo's 150,000-strong army has proved no match for a few hundred well-armed rebels.