Updated

Fighting swept through the capital of Central African Republic on Thursday, leaving dozens of casualties and posing the biggest threat yet to the country's new government. The U.N. Security Council authorized an intervention force to prevent a bloodbath between Christians and Muslims.

Witnesses and aid workers say at least 98 people are dead in Bangui after a day of clashes between the Muslim armed fighters who rule the country and a Christian militia who opposes them.

An Associated Press journalist counted 48 bodies at a mosque in a northern neighborhood late Thursday. Separately, Doctors Without Borders confirmed at least 50 people were dead at hospitals they are running.

The armed Christian fighters attacked the capital before dawn, in the most serious violence to hit Bangui since a March coup brought the Seleka rebel coalition to power. The former rebels are accused of committing scores of human rights abuses. The Christian militias who support the deposed president are implicated in massacres on Muslim communities.

Underscoring the chaos, even the president's and prime minister's homes were looted on Thursday.

The U.N. Security Council unanimously authorized increased military action by France and African troops and aimed at restoring security and protecting civilians in the volatile former French colony.

Speaking from the Elysee Palace in Paris, French President Francois Hollande promised that the 600 hundred troops in the country will be doubled "within a few days, even a few hours." The French leader said the Central African Republic was "calling us for help," and he "decided to act immediately."

In Bangui, people scurried indoors, including some who sought sanctuary inside a church. Inside a Bangui hospital, dozens of people with gunshot wounds lay on the floor or on wooden benches, waiting for hours to see a physician.

Hours after fighting broke out, Central African Republic's president, who was installed by Seleka earlier this year, said the clashes were over. By afternoon, the streets were empty of all but military vehicles and the four-wheel-drive pickup trucks favored by Seleka.

Prime Minister Nicholas Tiangaye confirmed his house had been looted, describing the attackers as a group of Seleka who arrived in three pickup trucks.

"It's true, my house was attacked and pillaged," he said, adding that his family was evacuated beforehand and were safe.

Babacar Gaye, the U.N. special representative for the Central African Republic, appealed for calm in a joint statement from the U.N., European Union, African Union and France.

Seleka is an unlikely group of allies who united a year ago with the goal of forcing President Francois Bozize from the presidency after a decade in power. After thousands of rebels besieged Bangui in March, Bozize fled and the insurgents installed their leader Michel Djotodia as president.

Djotodia has increasingly sought to distance himself from Seleka, which has been blamed for scores of atrocities in Bangui, killing and raping civilians and stealing from aid groups and orphanages. He has even less control in the distant provinces where anger over Seleka human rights abuses fueled the formation of the Christian anti-balaka movement several months ago. Balaka means "machete."

While the anti-balaka fighters include villagers defending their communities against Seleka attacks with artisanal hunting rifles and machetes, the group is believed to be receiving support from Bozize allies. The anti-balaka fighters also have been implicated in massacres on Muslim civilian populations, which also have suffered under the Seleka regime and say they are being unfairly blamed for Seleka's wanton destruction.

The U.N. Security Council resolution authorizes the deployment of an African Union-led force to Central African Republic for a year to protect civilians and restore security and public order. The AU force is replacing a regional peacekeeping mission whose presence has been mainly limited to the capital and a few northern cities.

The U.N. resolution also authorizes French forces, for a temporary period, "to take all necessary measures" to support the AU-led force known as MISCA, whose troop numbers are expected to rise from about 2,500 to 3,500.