UN helicopter gunships have attacked suspected rebel positions in eastern Democratic Republic of Congo, reports say.
The two sides have been involved in fierce fighting about 50 km (31 miles) north of the provincial capital, Goma.
The latest unrest began in April, with the UN and DR Congo government accusing neighbouring Rwanda of backing the rebels – a charge it denies.
More than 200,000 people in the region have been displaced by the conflict.
The gunships were despatched in support of government forces battling the M23 rebel group, in fighting centred around the Rutshuru area, about 50 km north of Goma.
Thousands of people are streaming out of villages, amidst heavy shelling. They told the BBC that government soldiers were also fleeing the battle. This is a conflict without traditional front lines, and fighting is taking place on multiple fronts, says the BBC’s Gabriel Gatehouse in Goma.
Military sources believe the rebels intend to march on Goma. However, a spokesman for the rebels denied this.
The UN has its biggest peacekeeping operation in the world in DR Congo. It has vowed to defend Goma. It first sent helicopter gunships to attack rebel positions on 12 July.
The rebellion is led by renegade general Bosco Ntaganda, who is accused by the UN of receiving military backing from Rwanda. He belongs to the Tutsi ethnic group like the top leadership in Rwanda, which fears the presence of rival Hutu militias in eastern DR Congo.
Eastern DR Congo has been plagued by fighting since 1994, when more than a million ethnic Hutus crossed the border into DR Congo following the Rwandan genocide.
Rwanda has since twice invaded its much larger neighbour, saying it was trying to take action against Hutu rebels based in DR Congo.