KINSHASA, Congo (CNN) -- Rebels trying to oust President Laurent Kabila of the Democratic Republic of Congo were on Tuesday fully in control of the key city of Kindu, following a military campaign that has seen the rebel influence spread significantly in the east of the country.

Rebels and senior loyalist military sources said that Kindu and its strategic airport had fallen late on Monday.

"We have control of the city and the airport," rebel commander Bob Ngoy Ngoy told reporters in Goma.

"They have taken Kindu," a senior loyalist military source, who asked to remain anonymous, told Reuters news agency. "Our troops have withdrawn. They have withdrawn in order. That's all I can say now. It's a war."

However, senior government military officials said the fall of Kindu did not amount to the end of the armed conflict, which has pulled in neighboring states who now have troops in Africa's third largest nation.

Zimbabwe, Angola and Namibia sent troops to fight for Kabila in August.

Rwanda and Uganda helped Kabila topple veteran dictator Mobutu Sese Seko in May 1997 but deny direct involvement in the latest conflict. They both claim to have legitimate security concerns in the east of the former Zaire.

The rebels now hold all the main towns in the east of the country, including the region's third-largest city of Kisangani.

Kindu had provided the government with a springboard to launch air strikes against rebel positions in the east.

The town is also on the main railway south to Lubumbashi and Kabila's copper-rich home province of Katanga.

The United Nations on Tuesday expressed concern about tens of thousands of refugees who had fled fighting in Katanga province in recent weeks.

Between 8,000 and 12,000 displaced people were now living in the southeastern towns of Kalemie and Uvira, according to a spokeswoman for the World Food`Program.

Most of the refugees were in a military camp in Kalemie, a rebel-held town 1,600 kilometers (1,000 miles) east of the capital Kinshasa.

Aid officials say they are worried that the displaced people may stay a long time and will be joined by others, thus creating health problems in an area where cholera is endemic.

Reuters contributed to this report.

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