French troops have reached the town of Bossangoa in the Central African Republic, which has been paralysed by communal fighting.
France is deploying 1,600 troops to help end the fighting in the country, alongside a larger African Union force.
French Defence Minister Jean-Yves Le Drian told the BBC the mission was aimed at creating stability to enable humanitarian aid to arrive.
The CAR has been in turmoil since the president was ousted in March.
Francois Bozize was overthrown by a rebel alliance known as Seleka in March. Its leader, Michel Djotodia, took over as president.
Armed gangs, mainly former Seleka rebels, now control most of the landlocked country.
Recently the violence in the chronically unstable country has taken on a sectarian tone, with Muslim and Christian communities pitted against one another.
French Defence Minister Jean-Yves Le Drian said that plans advanced rapidly due to the escalation in violence
French President Francois Hollande said he believed security could be restored within six months.
But when asked about the future role of Mr Djotodia, he said: "You cannot leave in place a president who has been unable to do anything and who has even let things happen."
Around 80 French troops reached Bossangoa late on Saturday.
Some 30 people have been reported killed there in the past three days and African peacekeepers have been struggling to help nearly 1,000 displaced civilians who have fled to their base.