It is down to a final stand by Gbagbo's loyalists and his Republican Guard, in Abidjan, against a force of northern rebels and Ouattara partisans that has swept the rest of the country out of the hands of the regime.
Predictably, once it came to this, the old hatreds and N-S divisions left over from the Ivoire Civil War have also spilled out. Looting and mistreatment of refugees are now being widely reported. *Here* is the BBC version, and *here* is AlertNet (from Reuters) with more about the fighting.
Meanwhile, the U.N. calls for calm and yet their peacekeepers are kept back at their base guarding foreign evacuees. France calls for a resolution, yet LICORNE force is also held back from acting. The de facto President, Gbagbo, encourages his men to fight and says he is still in the country (yet other reports place his family and key supporters already out of the country), while the internationally recognized President, Ouattara, awaits his invitation to move into the palace... once his allies are done turning Abidjan into looted rubble.
...because after months of ECOWAS ineptitude and international failure to back up their words, when push comes to shove... that's still how things are done there.