With the sound of heavy weapons fire echoing across the city from early morning from the battle front in the north east, the government urged the people via state radio and television to stay calm.
"The Congolese armed forces are conducting mopping up operations of armed elements who infiltrated the capital," a radio announcer said.
Sporadic bursts of automatic weapons fire could be heard closer to the city centre, witnesses said.
Diplomats reported a heavy military deployment near Kabila's residence, the Marble Palace, in the south west of the city, with numerous road blocks and security checks.
Kabila, who accuses former allies Rwanda and Uganda of invading in support of rebels who took up arms against him on August 2, returned to the city on Tuesday after spending just over a week in his southern home province of Katanga.
Information Minister Didier Mumengi played down the infiltration, telling state radio that enemy soldiers cut off from their rear base by Kabila's Angolan allies had taken refuge in the forest of Mikonga north east of the city.
"The time has come to end once and for all, to end the final convulsions of the invaders," he said.
Mumengi appealed on state radio and television for young people to form self-defence groups across the city of five million people in association with communal authorities.
"Dear compatriots, the government of public salvation invites you to remain calm. The Congolese armed forces, having decided to finish with the enemy once and for all, have things under control," he added.
Residents in the suburb of Masina, in the north east of the city, told Reuters that rebels had entered the area, telling everyone to stay at home. Witnesses said three government soldiers had been killed in the area.
Congolese and Zimbabwean forces had earlier blocked a rebel advance on the road approaching the city from the south west.
Rebel commanders told Reuters on Wednesday they had found another way of approaching the city.
Angola has sent troops, tanks and planes into the strategic western River Congo corridor linking the capital to the sea. They seized the rebel rear base in the garrison town of Kitona at the weekend and were advancing on the rebels from the rear.
"It's a desperate act but apparently well coordinated," one Western diplomat said of Wednesday's rebel operation.
Residents of Binza on the approaches to Kabila's residence reported that it was calm there but security was intense.
The radio said that the fighting started some time after dawn following the arrest of three infiltrators who denounced the presence of fellow rebels in the forest.
The sound of heavy artillery fire rang out around 8 a.m. (0700 GMT). It continued four hours later.
An early morning haze covered the city so it was unclear whether Kabila loyalists were using air strikes against the rebels as they had elsewhere on the western front. Witnesses reported at least one helicopter gunship flying over the city.
The government said after a cabinet meeting on Tuesday that Congolese forces and their allies had recaptured at string of towns in the west, including the main river port of Matadi.
"Today we can state with joy that the far west of our country has come back into the republic," Mumengi said. "Matadi, Kitona, Muanda, Boma and Banana have been retaken."
The recapture of Kitona, the oil town of Muanda, the smaller port of Boma and the naval base of Banana following the massive intervention of Angolan troops on the side of the government had already been reported. There was no independent confirmation that Matadi had been retaken.
With the rebels holding the giant Inga Dam in the west, Kinshasa awoke on Wednesday after a ninth night without electricity. In past days, power supplies returned later.
State radio broke into its programmes to offer its explanation of the explosions. It then continued with its usual daily fare of light music, sports and other reports.
State Television screened Disney's "Jungle Book" as part of its usual morning children's programmes.
Kabila ousted veteran dictator Mobutu Sese Seko with the help of Rwanda's Tutsi-dominated army, Uganda, Angola and a broad coalition grouping opposition figures in the former Zaire and other foreign allies in May 1997.
The rebels fighting Kabila hold Bunia, Goma, Bukavu and Uvira, the main towns in the east, and say that they control Congo's third city of Kisangani in the jungle interior.
- Reuters - Thomson Reuters Foundation
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