Forces loyal to the internationally recognised president, Alassane Ouatarra, captured the western city of Yamossoukro, which lies along their route to the commercial capital, Abidjan.
Many fear an imminent bloody battle for the presidency.
Te forces backing Mr Ouattara now control Yamoussoukro, Soubre, and Meagui.
There are also reports that they have entered the port of San Pedro, which handles the country's cocoa exports.
Our correspondetn John James is in the central town of Bouake that for years has remained the stronghold of Outtara's supporters.
He told BBC Network Africa's Akwasi Sarpong what the reaction has been to UN sanctions.