Fighting has again broken out in the east of the Democratic Republic of Congo, near the town of Bukavu, which was last week captured by rebels.
The UN's role is under scrutiny in eastern DR Congo
The fighting reportedly pits government troops against rebels, who were supposed to have withdrawn to barracks.
Belgium's Foreign Minister Louis Michel has mentioned the possibility of European Union peacekeeping troops going to eastern DR Congo.
The clashes around Bukavu threaten last year's deal to end five years of war.
One of the rebel commanders, Col Jules Mutebusi, says that the army forces advanced on the positions of his men.
He said the troops were led by Felix Budja Mabe, the army commander who left Bukavu last week.
The rebels accuse him of targeting ethnic Banyamulenge and insist that he be replaced.
Another rebel commander Brig Gen Laurent Nkunda has said that all his forces had left Bukavu, but the UN mission in the town could not confirm this.
Mr Michel said in the capital, Kinshasa, that the EU is expected to discuss sending troops later on Monday.
The EU approved a mission to Bunia in June last year - a first military deployment outside Europe.
He is continuing his "emergency mission" to the region by travelling to Rwanda and Uganda on Monday.
Rwanda has shut its border with DR Congo, after denying Congolese government allegations that it had backed the rebels.
In Uganda, he will meet Congolese Vice-President Jean-Pierre Bemba, who was backed by Uganda during the five-year civil war, reports the AP news agency.
Heightened security concerns have led to some UN staff being withdrawn from the capital, Kinshasa, and some UN peacekeepers being withdrawn from more isolated outposts in eastern areas.
On Sunday, two South African peacekeepers with the UN were killed and nine wounded when they were ambushed near Goma, some 120 km north of Bukavu.
A UN spokeswoman said witnesses identified the attackers as ethnic Hutu rebels, but this has not been confirmed. It appears unrelated to the occupation of Bukavu last week.
Gen Nkunda denies he is a mutineer
Rwandan Foreign Minister Charles Muligande told the BBC that the decision to close the border followed repeated lies about Rwanda's role in the fighting.
He said it would remain shut until the international community established a mechanism to clear Rwanda of the allegations that it was supporting rebel forces.
Diplomats have urged Rwanda to formally condemn the violence.
Gen Nkunda and his allies are members of the largest rebel group, the Rwanda-backed RCD, which controlled all of eastern DR Congo during the five-year war.
The commanders - who are ethnic Banyamulenge, related to Rwandan Tutsis - say government forces have been attacking members of their community.
He says he supports last year's peace deal, which set up a power-sharing government, including a vice-president from the RCD.
All the Congolese warring factions were supposed to unite as a single army, but progress has been slow.
This deal ended five years of war, which killed an estimated three million people dead and involved at least five foreign armies.