After the broadcast, explosions and gunfire could still be heard in the neighbourhood around the supreme court in Kinshasa's administrative district, close to one of Bemba's residences.
UN radio said one person had been killed and several injured in a building on the main avenue where some of the fiercest fighting took place.
A Reuters correspondent reported seeing one government soldier lying dead in the street.
"We're very worried by these violent clashes. We called for a ceasefire to be put in place before 18:00 [17:00 GMT] and we are still pushing for that now," said William Swing, head of the UN peacekeeping mission in DR Congo (Monuc).
"The two sides have accepted the principle, now it is a question of discipline."
|Bemba called on loyalist forces to|
return to their positions [AFP]
UN armoured personnel carriers patrolled the streets to protect civilians but did not intervene.
The clashes were the first in Kinshasha, a Bemba stronghold, since last year's elections.
Bemba's soldiers earlier chanted "Today we will not sleep" as government forces fired tank rounds towards them.
Ban Ki-moon, the UN secretary-general, was alarmed by the unrest, his deputy spokeswoman said.
"The secretary-general calls for an immediate halt to the fighting which threatens the lives of innocent civilians in the area and risks grave consequences for peace," Marie Okabe said.
Dozens of people were killed last year in fighting between Bemba's forces and Kabila's presidential guard before a run-off vote between the two men in October.
Kabila has ordered Bemba to reduce his security detail to 12 police officers. At the moment his armed guards number in the thousands.
Bemba's supporters say he is entitled to "an appropriate personal guard" under a UN-brokered deal signed before last October's vote.