"Given such numbers there is need for urgent humanitarian assistance, as some of the refugees are sick and have left all their belongings in Congo," Uganda Red Cross official Catherine Ntabadde told Agence France-Presse on Sunday.
Tallies made late on Saturday estimated 55 000 refugees had crossed the border, up from 30 000 the day before, she added.
Refugees have streamed across the border into western Uganda's Bundibugyo district since the attack on Thursday, although the numbers of new arrivals crossing on Sunday had slowed to a trickle.
"Many new arrivals are also reported to be staying in the community," United Nations refugee agency official Karen Ringuette said. "New arrivals are staying at five primary schools and various other sites."
Thousands crowded into the grounds of schools in Bundibugyo — about 20km from the border with DRC — offered as a temporary shelter, with many building makeshift shelters or sleeping out in the open.
The Red Cross are working with the United Nations and other aid agencies to set up a camp further inside Uganda, although many refugees appeared reluctant to leave.
"The [Ugandan] government has found a transit camp eight kilometres from Bundibugyo town … There we can start registering them afresh," Ntabadde said.
However, an AFP photographer said that long lines of refugees crossing into Uganda seen in recent days had declined, and that large crowds were waiting to return back into DRC.
Ugandan police however were encouraging people to move to the new camp, refugees said.
The town of Kamango in the northernmost part of DRC's North Kivu province was attacked and briefly occupied on Thursday by a Ugandan-led rebel group, the Allied Democratic Forces (ADF).
Residents of Kamango said that public buildings and the hospital had been pillaged but no toll was given of possible casualties.
In Bundibugyo, refugees carried their belongings piled on their heads, including rolled-up mattresses, cooking pots and chickens.
Some refugees complained that while they had seen food delivered by the UN World Food Programme, they had not yet received any.
"We have nothing to eat, because when we ran from the rebels we could only grab what we had around us and could carry," said Teresa Zaki, who fled from Kamango on Thursday.
The ADF was formed in the mid-1990s in the Rwenzori mountains in western Uganda, close to the DRC border.
Part of the ADF is now based in DRC after Ugandan government forces attacked their bases two years ago.
It has been relatively quiet in recent years, and it was not immediately clear what sparked the ADF attack on Kamango. – AFP