Soldiers in the eastern Democratic Republic of Congo are closing in on one of the last strongholds of rebel group M23.
Government officials said Wednesday that heavy fighting had erupted near the eastern town of Bunagana, near the Ugandan border.
U.N. refugee agency officials say some 2,000 Congolese civilians have fled into Uganda, with about 6,000 more preparing to cross the border.
In an interview with VOA, UNHCR Uganda spokeswoman Lucy Beck said the first wave of civilians fled in anticipation of fighting, but the situation changed on Wednesday.
"The people who have arrived today, the biggest majority of them have come because they are in areas that are being attacked. So, many have seen the fighting. They have heard the bullets and that's why they have crossed."
Beck says relief workers are struggling to cope with the influx of refugees.
"It is a struggle. At the moment, we have in place assistance for about 5,000 people so what we are doing right now is working on, particularly, more shelters so that we can provide a roof over people's heads and also working on the hygiene situation, providing latrines for people to use. These are the two key areas."
The Congolese army has seized several towns from M23 in Congo's North Kivu province since fighting began last Friday.
M23 consists of rebel fighters who joined the Congolese army in a 2009 peace deal but later defected after complaining of poor treatment.
Earlier this month, the U.N. said the peace talks in Uganda between the government and the rebels had stalled. Negotiators said the two sides remained apart over proposed amnesty for the rebels.