United Nations attack helicopters have fired rockets near Laurent Gbagbo’s official residence in Ivory Coast’s Abidjan.
Forces belonging to his presidential rival Alassane Ouattara claim to have taken the building although Gbagbo’s whereabouts are unclear.
French helicopters had earlier taken part in UN-led operations aimed at knocking out Gbagbo’s heavy weapons.
Abidjan is Gbagbo’s last stronghold, with his rival’s position previously limited. But Ouattara’s win in November’s presidential election is recognised by the UN.
His forces have taken much of the rest of the country and have now poured into the city in a bid to push Gbagbo out of power.
The increasingly brutal violence between the two sides has triggered the intervention by the UN and Ivory Coast’s former colonial power France. Their brief is to protect civilians although at least 1,500 have been killed since November’s poll.