Forces loyal to Alassane Ouattara, whom the international community has recognized as the winner of a contested presidential election in Ivory Coast, attacked the residence of the incumbent president on Friday.
Ouattara loyalists entered the commercial capital Abidjan on Thursday, and fighting between the rival factions waged for hours, Reuters reported.
The move into Abidjan comes after a week of Ouattara loyalists making strong gains across the country as they battle for control over Ivory Coast away from Laurent Gbagbo, who has refused to step down since an election in November.
Abidjan, the main population center in Ivory Coast, is a Gbagbo stronghold.
The attack on Gbagbo's residence was reported by Ouattara loyalists and confirmed by a military source.
Battles were also reportedly under way in the district of Cocody, where the presidential residence is located, and around a barracks in Ajame to the north, reesidents told BBC
"His house is under attack. That's for sure. There is a resistance, but it's under attack," Ouattara spokesman Patrick Achi told Reuters.
"(Gbagbo) hasn't shown any signs of giving up. I don't think he will see the game is up, because he really believes God will save him."
There were also reports that Ouattara supporters had seized control of the country's state television, but Gbagbo loyalists denied this.
Ouattara's loyalists, the Republican Forces, have swept south over the past week as they have met little resistance from Gbagbo forces and have seized about a dozen towns, PBS reported.
They captured one of the major cocoa-exporting ports, San Pedro, as well as the political capital, Yamoussoukro, in the past two days, Bloomberg reported.
Gbagbo's forces are expected to put up a strong fight in Abidjan, raising fears of more bloodshed.
“Abidjan is on the brink of a human rights catastrophe and total chaos,” Salvatore Sagues, a West Africa researcher for London-based Amnesty International, told Bloomberg. “The international community must take immediate steps to protect the civilian population.”
The U.N. Security Council voted unanimously Wednesday to impose sanctions on Gbagbo in an effort to force him from power.
Gbagbo's forces have been accused of launching attacks and committing a range of rights violations against civilians since the election.
The United Nations estimates that one million people have fled their homes as a result of the post-election violence.
About 100,000 of those have fled to Liberia, raising fears that the crisis in Ivory Coast will become a threat to regional stability, the New York Times reported.
“It’s a serious threat to the stability of Liberia and, I might say, to the stability of all neighboring countries,” Liberian President Ellen Johnson Sirleaf told the Times.
“There’s been a lot of investment for peace in this subregion; we’re beginning to see the result of that investment,” she added. “If nothing is done to resolve the crisis, all of these efforts will be undermined.”
-- Hanna Ingber Win