"The president is not in Kinshasa," the high-level government adviser told The Associated Press on condition of anonymity. "I can't tell you any more than that."
Asked if Kabila intended to return, the official would only say: "For that, we'll have to wait and see."
A Western diplomatic source in Paris, speaking on condition of anonymity, said Kabila is in Lubumbashi, his former rebel base, but had no further information on what his plans were.
With rebel forces driving toward Kinshasa from the west, the jittery Congolese capital awoke Friday without electricity, radio, television, or newspapers - and reports their leader had fled.
State radio in Kinshasa came back on air on Friday, a day after being silenced by a general electricity outage caused by a rebel takeover of power distribution.
The rebels on Thursday switched off the power supply to Kinshasa and the nearby Congo Republic capital of Brazzaville, as well as copper and cobalt mines in Congo's southern Shaba Province. Electricity supplies were restored in several parts of Kinshasa on Friday after a gap of almost 24 hours, state radio in the Democratic Republic of the Congo reported.
The outage crippled water and petrol supplies in Kinshasa, a sprawling city of more than 6 million people.
Congolese recruits dance along the roadside in Kinshasa (AP)
"This is the end," said Jean-Pierre Mwenge, standing amid a crowd of people searching for transport to leave the city. "Now I'm alone, and this will be the end."
Asked where he would go, Mwenge just shrugged.
The United States was preparing for the emergency evacuation of its citizens, while foreign airlines have stopped service to Kinshasa in the wake of the escalating crisis.
A primary exit route across the Congo River to Brazzaville, the capital of neighboring Republic of Congo, was closed days ago, with all traffic across the water stopped and port facilities shut.
In a stunning move, the rebels, led by Tutsi and Rwandan fighters and disenchanted members of Kabila's military, quickly captured key towns in the east and west.
The rebels also said some of their troops had advanced as far as Kasangalu, 18 miles southwest of the capital.
Rebel leaders in Goma in eastern Congo said Kinshasa was now in their sights.
Refugees pass through a military checkpoint (AP)
In the United States, Pentagon spokesman Kenneth Bacon said two Marine amphibious warships had been dispatched to the Atlantic waters off Congo in case they are needed to evacuate U.S. citizens living there. It will take nine or ten days for the ships to reach the area.
Kabila's propaganda campaign accusing neighboring Rwanda of staging an invasion and orchestrating the rebel uprising was abruptly cut off Thursday when power to the city was severed. Rage and anger at Rwanda were giving way to fear, as many people speculated over their fate.
"It's time to pray now," said Amina Nzuze, a waitress. Her restaurant, like many small businesses, was shut for fear of looting during the night.
Rumors of ethnic attacks by both sides only worsened the fear of what will happen if the rebels arrive.
On Thursday, Congo and Rwanda accused each other of attacks against Hutu and Tutsi civilians.
The Rwandan government called on international agencies to intervene and save ethnic Tutsis it said were being persecuted by Congolese authorities, state-run Radio Rwanda reported.
In Kinshasa, the human rights minister said Rwandan troops were attacking ethnic Hutus living in eastern Congo.
Kabila's government denies it is persecuting Tutsis, but authorities in the capital acknowledge a number of civilians have been arrested on suspicion of complicity with the rebels.