"There are firing heavy arms and we are hearing automatic fire," a witness said early Monday, speaking from Abidjan's chic Cocody suburb where the presidential complex is located and where Gbagbo has been holed up in a bunker.
He located the fighting in the area between the headquarters of the state television network and the gendarmerie training school, both Gbagbo bastions, but said there were no attacks on the presidential residence.
United Nations troops and French forces attacked positions of pro-Gbagbo troops overnight after a luxury hotel serving as the base of UN-recognised president Alassane Ouattara came under fire.
A spokesman for the UN mission in Ivory Coast (UNOCI) said its peacekeepers and France's Licorne force had aimed to destroy heavy weapons that were being used against civilians.
Missiles were fired at Gbagbo's residence shortly before 11:00 pm (2300 GMT) yesterday, a source close to the operation said. The presidential palace and military camps were also targeted.
UN chief Ban Ki-moon confirmed he had ordered the attack and repeated UN accusations that the Gbagbo camp had used an offer of talks he made last week "to regroup their forces and redeploy heavy weapons".
His forces had since resumed heavy weapon attacks on civilians, on the UN peacekeepers' base and on Ouattara's base at the Golf Hotel, he added.
"These actions are unacceptable and cannot continue," Ban said in a statement. France today said its military had taken part in the raids at the UN chief's request.
"The Secretary General of the United Nations asked the president of the republic to continue the participation of French forces in the operations ... to neutralise heavy weapons used against the civilian population," the French presidency said in a statement.
Witnesses said at least four missiles had been fired towards the residence and three helicopters had fired on the presidential compound.