Senior Ugandan and Rwanda officials are due to meet in the region on Monday to discuss the fighting, which broke out on Saturday in Kisangani in north-east Congo.

A gun battle began at the airport and later continued during street battles in the city.

Chris Simpson: Allegations that Ugandan commanders were sabotaging the war effort

BBC's Correspondent in Kigali, Chris Simpson, says reports of continued fighting suggest the confrontation between Ugandan and Rwandan troops is far more serious than anticipated.

Uganda and Rwanda have been involved in the Congolese conflict since they began supporting rebels fighting the government of Laurent Kabila.

Rwandan commanders say Ugandan troops stationed at Kisangani's main airport opened fire on Rwandan positions a short distance away on Saturday night.

The Rwandan troops returned fire, and are said to have wounded several Ugandan soldiers.

The Rwandans accused Uganda of provoking an incident in an attempt to secure control of the airport, 25km (15 miles) east of the city, where supplies are flown in daily.

"The Ugandan army deployed troops all night to surround the airport, and they tried to block us in, they fired and there was a skirmish," said Rwandan Government spokesman Lieutenant Colonel Wilson Rutayisire.

"The Ugandan army then rallied again, directly attacking our troops, but we pushed them back," he said.

Rival factions

Rwanda and Uganda support opposing rebel factions in Congo who have been waging a year-long rebellion to oust President Laurent Kabila.

Relations deteriorated between the two armies when the main Congolese rebel movement, the Congolese Rally for Democracy (RCD), split a few months ago.

The two countries signed a peace agreement with President Kabila last month.

Wamba: Supported by Uganda after RCD split

Former rebel leader Ernest Wamba dia Wamba was ousted as head of the RCD in May, but refused to step down.

With Ugandan backing, Mr Wamba established new headquarters in Kisangani, where Ugandan forces have been flying in troops to bolster him and his supporters.

The RCD's dominant faction, backed by Rwanda and headed by Mr Wamba's successor Emile Ilunga, is based in Goma, in eastern Congo.

A senior military commander from Dr Ilunga's wing of the RCD told the BBC that all Ugandan troops had to leave Kisangani as soon as possible, if calm was to be restored.

But a spokesman from Professor Wamba dia Wamba's faction accused the Rwandans of trying to provoke a confrontation in Kisangani and hijacking the rebellion for their own ends.

Ministers in Kigali have expressed bewilderment and frustration at the rebel in-fighting, saying it is a serious error of judgement at best.