Thousands of refugees have registered at a transit centre in Uganda after fleeing fighting between the army and mutineers in Democratic Republic of Congo, a UN refugee agency official said Wednesday.

More than 1,000 refugees arrived at the centre near the border on Tuesday alone, adding to the growing number of Congolese who have sought help since heavy clashes broke out earlier this month, Sakura Atsumi, deputy UNHCR representative in Uganda, said.

"Since 11 May we registered 8,520 refugees as of yesterday (Tuesday) night and we are still registering," Atsumi said, adding that the UNHCR had already moved two convoys of refugees to a settlement further from the border.

Ugandan officials said earlier that thousands more Congolese were likely staying along the border, given shelter by local people and waiting to see if fighting dies down before deciding to register with the authorities.

The Ugandan authorities said Wednesday that they had registered around 18,000 Congolese refugees in camps around the country. They include both those who arrived late last year and some 10,000 who have crossed since April, according to David Kazungu, Uganda's commissioner for refugees.

In neighbouring Rwanda, the number of refugees arriving from DRCongo has dropped markedly since spiking in early May, said UNCHR spokeswoman in Rwanda Anouck Bronee.

"Currently, approximately 150 on average cross the border into Rwanda every day," Bronee said.

In total 8,885 Congolese refugees have arrived at a transit centre close to the border town of Gisenyi since April 27, Bronee said.

Fresh clashes erupted in DRCongo over the weekend between the army and a group of mutineers known as the March 23 movement in the violence-wracked eastern province of Nord-Kivu, close to the border with Uganda.

The mutineers are former rebels who were integrated into the army under a 2009 peace deal -- after which the group is named -- but started to defect en masse, complaining of poor treatment.

Kinshasa accuses former rebel leader Bosco Ntaganda, wanted by the International Criminal Court for enlisting child soldiers, of leading the mutiny. The fugitive general denies the allegation.