Rwandan President Paul Kagame will not attend the summit in Uganda seeking a solution to the conflict in eastern
Democratic Republic of Congo.
"Kagame is not coming," James Mugume, a senior official in the Ugandan foreign ministry, saying the president would be represented by Rwandan Foreign Minister Louise Mushikiwabo at the summit on Saturday.
Mugume gave no indication as to why Kagame, whose government the United Nations accuses of backing DR Congo's M23 rebels, a claim Kigali rejects had decided not to attend.
Sources in Brazzaville and Kigali said the Republic of Congo's President Denis Sassou Nguesso would fly into the Rwandan capital Saturday afternoon for talks with Kagame.
Members of Sassou's delegation had already arrived Friday in Kigali.
Meanwhile DR Congo President Joseph Kabila arrived late morning at Munyonyo resort on the outskirts of Kampala, where the summit will be held.
Ugandan officials had earlier said that both Kagame and Kabila would attend and that without them the summit would be "meaningless".
President Mwai Kibaki of Kenya and Tanzania's Jakaya Kikwete were also in Kampala for the summit, along with host Yoweri Museveni of Uganda, Mugume said.
A delegation from the M23 rebels was also in Kampala, but not at the summit venue, and was expected to hold separate talks with Museveni later in the day.
Kabila and Kagame met on Tuesday and Wednesday, hours after the rebels seized the regional capital of Goma, issuing a joint statement with Museveni calling for the M23 to stop its offensive and pull out of the key eastern city.
The International Conference on the Great Lakes Region (ICGLR) has held multiple summits in recent months on the conflict in eastern DR Congo, but none resulted in a significant breakthrough.
The summit comes as the United Nations has expressed shock at the sight of thousands of civilians fleeing a rebel advance in the eastern DR Congo and appealed for access to help those caught up in the violence.
Thousands of civilians are fleeing the town of Sake, which was taken over by the M23 rebels battling government troops threaten to overrun Goma.
Al Jazeera's Nanazine Mosheri, reporting from Sake, said the town of Sake is currently calm.
"The M23 has Sake very much firmly under their control, the aim now is to take the surrounding the areas under their control, The fact that there is no fighting today (Saturday) maybe because people are waiting for the talks in Kampala."
The rebels' advance comes days after they took Goma, the biggest city in North Kivu province, and have vowed to expand their territorial control and even seize the capital, Kinshasa, although the city is 1,574km away.
The fighting has sparked fears of a wider conflict erupting in the chronically unstable region, and the rebels have largely ignored calls made in a joint communique by the presidents of DR Congo, Rwanda and Uganda to pull out of Goma.
The UN estimate that 140,000 people in and around Goma have been displaced in recent fighting.
Aid officials said the fighting has made camps for people displaced by earlier conflicts inaccessible, with food and medicines running short.
Fears of refugee crisis in DR Congo
A spokesman for the UN peacekeeping force in the country, known under the acronym MONUSCO, described the situation in eastern DR Congo as "alarming".
"The M23 are now present in Sake, with reports indicating that they may be on the move toward Masisi territory, which is their stronghold," Kieran Dwyer said in a statement.
MONUSCO has airlifted dozens of local leaders and rights activists who feared for their lives out of rebel territory, Dwyer said,The UN has an estimated 6,700 troops in North Kivu backing up government forces under a Security Council mandate to protect civilians. They have been criticised for not directly confronting the M23.
The UN mission was also verifying reports of civilians wounded or killed due to the recent fighting in Goma and Sake, he added.
"There are also reports of targeted killings and health personnel being abducted by the M23. Reports of recruitment and abduction of children by the group continue," he said.
M23 military leader Bosco Ntaganda is wanted for war crimes by the International Criminal Court.
Meanwhile, in Kinshasa, protesters accused the rebels of abuses including the rape of pregnant women. Hundreds of women, clad in black, marched on the UN mission's headquarters, carrying banners calling for peace and criticising the country's small but militarily powerful neighbour. "No to Rwanda!" read one.
The M23 fighters are widely thought to be backed by neighbouring Rwanda.
The UN Security Council has expressed "concern at reports indicating that external support continues to be provided to the M23, including through troop reinforcement, tactical advice and the supply of equipment".
The council did not name Rwanda whose experts have previously accused it of backing the rebels, who share the same Tutsi ethnicity with Rwandan President Paul Kagame but are Congolese.
The rebellion was launched eight months ago by mutinous troops accusing the government of failing to stick to a 2009 deal with fighters to end a previous conflict.
The rebels take their name - M23 - after that peace agreement which was signed on March 23, 2009.