Clashes ripped through the Central African Republic’s capital of Bangui on Thursday, as the United Nations authorized sending more French and African soldiers to contain the escalating bloodshed, which has killed hundreds and triggered warnings of genocide.

Witnesses and aid agencies said scores of people were killed or injured in Thursday’s violence, the worst to strike the capital since a March coup, as Muslim and Christian militias battled in the streets. Witnesses described seeing bodies in the streets, many of them hacked to death with machetes or knives.

“We heard shooting most of the morning — we’ve had to hunker down at home as it’s just too dangerous to go out,” Renee Lambert, the country director for the Baltimore-based aid agency Catholic Relief Services, said in an e-mail. “I’ve been communicating with national staff and colleagues all day and I’ve been told of people being shot and hacked to death, just streets away from where I am. It’s devastating — the worst violence I've seen in the 18 months I’ve lived here.”

The aid agency Doctors Without Borders reported that its employees saw 50 bodies taken to the morgue.

The Central African Republic, a landlocked nation of about 5 million people, has been gripped by instability since independence in 1960, fueled by military coups and brutal regimes. The most recent period of chaos began when the Muslim rebels ousted President François Bozizé in March and installed Michel Djotodia, the first Muslim leader in the Christian-majority nation.

Known as Seleka, the rebels embarked on a campaign of killing, kidnappings and other human rights abuses, mainly against Christian communities. The violence sparked the rise of Christian vigilante groups known as “anti-balaka.” “Balaka” means “machete” in the local language. The groups are accused by human rights groups of committing atrocities against Muslim communities.

The Christian militias attacked Bangui at dawn Thursday, armed with rocket launchers, guns and machetes, according to news agency reports. That triggered retaliation by the Seleka rebels. In the chaos, even the president’s and prime minister’s houses were looted, the Associated Press reported. The fighting subsided by mid-morning but nevertheless was a sign of the increasing instability in the former French colony.

Hours later, the U.N. Security Council unanimously approved a French-sponsored resolution to bolster the French and African Union forces already present in the country. The 2,000-strong African contingent is expected to expand to 3,600, while France is expected to increase its force to 1,200 soldiers. The resolution also provides a so-called Chapter VII mandate, which in theory gives the troops greater power to protect civilians and restore security

Both the United Nations and France have said the bloodshed could spiral into large-scale ethnic and sectarian violence, and French Foreign Minister Laurent Fabius warned last month that the country was “on the verge of genocide.”

The Obama administration has pledged $40 million to support the African Union force and said in a statement that the Security Council resolution “is an important step in preventing further atrocities or an escalation of the violence.”

Gerard Araud, the French ambassador to the United Nations, told reporters after the Security Council meeting that “history has taught us the worst may happen. History has taught us the Security Council needs to act.”

In Bangui, many feel the same way. “People have been living in a perpetual state of fear and uncertainty for nearly a year now,” Lambert said. “Hearts can’t take much more breaking in this place. The time to act is now.”