ABIDJAN, Cote d'Ivoire - Forces loyal to Cote d'Ivoire presidential claimant Alassane Ouattara laid siege to incumbent leader Laurent Gbagbo's residence on Thursday, after an attempt to pluck him from his bunker met with fierce resistance.

A UN spokesman said negotiation with Gbagbo is still going on to seek his stepping down.

Fighting continued in Abidjan as Ouattara's forces tried to unseat Gbagbo, who has refused to cede power after losing a November election to Ouattara according to UN-certified results. Sporadic explosions broke the silence of one of the quieter nights since Ouattara's soldiers arrived in the economic capital a week ago, a Reuters witness said.

Gbagbo's forces also roam the streets and broke into the Japanese ambassador's residence overnight, forcing him and seven other employees to take shelter in a safe room before French and United Nations forces rescued them by helicopter, Japanese media reports said.

French forces also destroyed military vehicles belonging to troops loyal to Laurent Gbagbo during the helicopter-borne mission that rescued the Japanese ambassador.

A Gbagbo adviser based in Paris said Ouattara forces had renewed an assault on Gbagbo's residence late on Wednesday with support from UN and French helicopters. His statement could not be independently verified.

Ouattara forces had tried to storm the residence in the upscale Cocody neighborhood earlier on Wednesday after talks led by the United Nations and France to secure Gbagbo's departure failed, but they were pushed back by heavy weapons fire, a western diplomatic source who lives nearby said.

The former colonial power in Cote d'Ivoire, France has taken a leading role in talks to persuade Gbagbo to hand over to Ouattara and end the standoff over the contested election.

UN peacekeeping department spokesman Nick Birnback told AFP Gbagbo remained in contact with international representatives. "Discussions continue with the UN using its good offices to the fullest extent possible," he said.

Reuters-AFP