The U.N. Security Council on Thursday unanimously approved a nearly 12,000-strong U.N. peacekeeping force for Central African Republic, where mounting violence between Christians and Muslims has brought killings, torture and sexual violence.

The 10,000 U.N. troops and 1,800 police will take over from 5,000 African Union soldiers -- but not until Sept. 15. A separate 2,000-strong French force in the Central African Republic was authorized to use "all necessary means" to support the new U.N. force.

How much protection U.N. troops will be able to offer is an open question. Keeping civilians safe throughout the Central African Republic, especially in rural areas, is already proving a difficult, if not impossible task. The country is the size of Texas, many roads have not been repaved since independence from France in 1960, and many of the people escaping violence have fled into the bush.

The country has been in chaos since a March 2013 coup, when mostly Muslim rebels seized power and set up a brutal regime. Christian militiamen attacked rebel strongholds in early December. As the rebel government crumbled in January, the Christian militiamen stepped up the violence, forcing tens of thousands of Muslims to flee.

On the streets of the Central African Republic's capital, Bangui, reactions to the U.N. deployment were muted.

Cyrius Zemangui-Kette, 25, who is unemployed, said U.N. troops should have been sent in long ago, but the international community dragged its feet and now things have gotten worse.

"They say they'll arrive in September," he said. "Until then, lots of Central Africans will continue to die, so who are they coming to save?"

Clashes between Christian and Muslim fighters in the central town of Dekoa that began Tuesday have left at least 30 people dead, a priest said Thursday. Most of the victims were civilians, killed by Muslims who fired into a crowd of people they mistook for Christian militants, Father Everaldo De Suza of the Saint Anne parish said. A Christian commander confirmed the fighting but denied that his forces had started it.

Speaking at U.N. headquarters in New York, Secretary-General Ban Ki-moon called for an end to the killings, and Toussaint Kongo-Doudou, Central African Republic's foreign minister, said the new resolution "lays the foundation for a solution and a way out of the crisis."

France, the country's former colonial power, took the lead in mobilizing international support to address the crisis but its ambassador, Gerard Araud, said the security situation remains volatile.

"African Union troops supported by the French troops are doing tremendous work to protect the civilian population but it's not yet enough," Araud said after the vote. "The resolution we have just adopted is a key turning point."

U.S. Ambassador Samantha Power, who returned Thursday morning from her second visit to the country in less than four months, also praised the resolution and added: "I can personally attest to the critical urgency of bringing more security to the Central African Republic."

Power went to the Central African Republic after leading the U.S. delegation to the 20th anniversary commemoration of the Rwanda genocide, which she said "taught us the price of inaction in the face of mass violence."

The resolution expresses serious concern at multiple violations of human rights and humanitarian law committed by both former Seleka elements and anti-Balaka militia including killings, torture and sexual violence against women and children. It also demands that all militias and armed groups put down their arms "and release children from their ranks."

The Security Council wanted a strong mandate and the resolution authorizes the new U.N. force to protect civilians and support the disarmament of combatants and the restoration of peace and law and order. It also authorizes the mission to help investigate violations of human rights and humanitarian law by armed groups and arrest perpetrators.

While U.N. peacekeepers and police will not take over until Sept. 15, the resolution immediately establishes the U.N. mission, to be known as MINUSCA. It will take over all activities of the U.N. political office, including supporting the country's political transition and giving logistical support to African Union force on the ground.

The resolution urges the transitional authorities to accelerate preparations for free and fair elections no later than February 2015.

Philippe Bolopion, United Nations director for Human Rights Watch, urged the United Nations and member states to make the U.N. force a reality on the ground quickly, "including by providing carefully vetted troops, so the U.N. mission itself does not become embroiled in any allegations of abuses."

"This resolution doesn't mean that the U.N. cavalry is going to roll in and save the day," he warned.

Associated Press Writer Hippolyte Marboua contributed to this report from Bangui, Central African Republic.