UN peacekeepers in the Democratic Republic of Congo have opened fire on a rebel faction of the Congolese army.
UN peacekeepers are struggling to end the fighting in Bukavu
The clash occurred in the eastern border town of Bukavu, where the UN has been trying to end clashes involving regular troops and rebel soldiers.
The unrest has caused about 2,000 people to flee to neighbouring Rwanda in recent days.
On Friday a UN helicopter gunship fired a rocket at supporters of former rebel commander Colonel Jules Mutebusi.
The incident came on the third day of fighting between his men and other units of the Congolese army.
Looting and raping
Under a peace deal agreed last year, all the Congolese warring factions were supposed to unite as a single army.
But violence between the two sides first broke out on Wednesday evening - there are contradictory reports over who started the fighting.
Former rebels are being integrated into a new national army
On Friday UN peacekeepers accused Colonel's Mutebusi's troops of looting and raping civilians.
The UN has warned that the rebel soldiers will be forcibly disarmed if they do not return to their barracks.
The BBC's Robert Walker in Bukavu says the latest clashes underline the continuing difficulties in integrating former rebels into a unified national army.
Colonel Mutebusi and most of his troops are from the Banyamulenge ethnic group.
Most of the refugees who have arrived at a camp near the town of Cyangugu in Rwanda are also Banyamulenge.