Ivory Coast presidential claimant Alassane Ouattara's forces battled loyalists of his rival Laurent Gbagbo near his Abidjan residence on Friday, having seized control of state television overnight.
With the television station cut off, no news emerged from Mr. Gbagbo's camp, which has been hit by a number of high-level defections in the military, but a Paris-based adviser said his surrender was "out of the question".
The main city in the world's top cocoa grower has turned into a war-zone since forces loyal to the internationally recognized president marched in on Thursday after a swift push south aimed at ousting Mr. Gbagbo, who has refused to quit since a Nov. 28 election that UN-certified results said he lost.
The African Union called on Mr. Gbagbo to hand over power immediately.
Hundreds of foreigners were taken to a French military camp for their protection after they were threatened by looters. Rights and aid groups have warned of appalling conditions.
The United Nations also called on Mr. Ouattara to rein in his forces, citing what it said were unconfirmed reports they had abducted and mistreated civilians.
"We can hear shooting and see soldiers moving but there are also armed civilians running in the streets," said Camara Arnold, a resident in Cocody, the leafy neighbourhood that is home to the state television building and Mr. Gbagbo's residence.
"Fighting is still going on all around Gbagbo's residence," Ouattara spokesman Patrick Achi told Reuters, hours after he said pro-Ouattara forces attacked.
Mr. Achi said he didn't know if Mr. Gbagbo was still inside but overnight he said Mr. Gbagbo was there and looked like fighting on.
Mr. Gbagbo's camp in Abidjan was not available for comment but Alain Toussaint, a Paris-based adviser of Mr. Gbagbo's, said he would not give up. "He will not surrender. It is out of the question," he added.
Mr. Toussaint said pro-Gbagbo forces had re-taken control of state broadcaster, RTI, which has been off the air since Thursday. But residents said Mr. Ouattara's forces were in control, with Mr. Gbagbo loyalists confined to a small pocket.
One resident said overnight fighting was so heavy it shook the earth.
French medical charity said it had become impossible for people in Abidjan to obtain medical care in the current conditions and U.K.-based Amnesty International said the city was "on the brink of ... total chaos".
French forces have taken about 500 foreigners, including 150 of its own nationals, to a military camp in Ivory Coast after they were threatened by looters.
Mr. Gbagbo has been in power since 2000. His mandate ran out in 2005 but the presidential election was delayed until 2010 because of instability in the country.
A Sorbonne-educated history professor who prides himself on being in touch with ordinary Ivorians, he rose to prominence as firebrand lecturer who challenged the autocratic rule of Ivory Coast's first post-independence president.
The four month standoff since the election has killed hundreds and rekindled the country's 2002-3 civil war. About 1 million have fled Abidjan alone and 122,000 more have crossed into Liberia, according to the United Nations.
Earlier this week, Mr. Ouattara's forces advanced from several directions, taking the capital Yamoussoukro and the cocoa port of San Pedro with little resistance.
Some of Mr. Gbagbo's top officers, including the head of his armed forces and gendarmerie, have abandoned him but an unknown number appear to be putting up stiff resistance and Mr. Ouattara's forces could get sucked into bloody urban warfare with his hard-core supporters, some of whom are recently armed civilians.
The capture of San Pedro, which ships half of the country's production, could kick-start the flow of beans that dried up in January due to sanctions, but diplomats said any easing of EU measures would take several days.
Mr. Ouattara has rejected appeals by Mr. Gbagbo for a ceasefire or further dialogue.
UN troops were in control of Abidjan airport after Gbagbo forces abandoned it, a security source and UN sources said.
An internal UN report, seen by Reuters, also said pro-Gbagbo forces had abandoned a blockade of a hotel Mr. Ouattara had been restricted to. It also said peacekeepers had exchanged fire with Gbagbo loyalists in several parts of the city.
Mr. Ouattara has ordered a three-day overnight curfew and ordered the closing of land, air and sea borders.
At least 494 people have been confirmed killed since the standoff began, according to the United Nations, but, given the scale of fighting, the real figure is likely to be much higher.