BANGUI -- The U.N. humanitarian chief on Thursday said that more troops are needed on the ground in volatile Central African Republic, where Muslims have been slain in the streets of the capital despite the presence of thousands of French and African peacekeepers.

In wrapping up her three-day visit to the country, U.N. Under-Secretary-General for Humanitarian Affairs and Emergency Relief Coordinator Valerie Amos told reporters she and her colleagues "were shocked by what we saw." The group's trip north of the capital was delayed on Wednesday amid heavy fighting and gunfire that blocked all roads to the airport.

Amos acknowledged the strong efforts being undertaken by the nearly 6,000 peacekeepers from African countries known as MISCA along with the French, who already have sent 1,600 forces and have promised 400 more. Despite those soldiers, she said it was clear more needs to be done.

"Despite the good job that the MISCA and Sangaris (French) forces are doing that there are not enough troops on the ground," she told reporters in the capital of Bangui.

Many have called for the African Union-led peacekeeping force to be transformed into an official U.N. peacekeeping mission, though U.N. officials say such an effort could take up to six months to have on the ground. That could be too late for the thousands of Muslims who fear for their lives after Christian militia fighters went on a deadly rampage killing anyone suspected of having supported a now-defunct Muslim rebel government accused of carrying out scores of atrocities.

Central African Republic, long one of the world's poorest and most unstable countries, plunged deeper into chaos nearly a year ago when the Muslim rebels from the north invaded the capital and overthrew the president of a decade. The rebels pillaged neighbourhoods, raping and killing people with impunity for months, giving rise to the Christian militia. Those fighters attempted a coup in early December, and violence between the two communities exploded in the days that followed.

The president installed by the Muslim rebels has since gone into exile, and a nascent civilian government is attempting to restore order.

Critics say that the international peacekeeping mission, though, has failed to sufficiently protect civilians in many remote areas outside the capital in this nation of 4.6 million people. In other cases, Burundian peacekeepers stood by as a group of soldiers brutally stomped and stabbed to death a man they accused of being a rebel. The man's corpse was later dragged through the streets, dismembered and set on fire.

Amid such violence against the country's Muslims, the world's largest bloc of Islamic countries agreed Thursday to send a high-level fact-finding mission to Central African Republic and to appoint a special representative to co-ordinate efforts with the African Union and the United Nations.

The Organization of Islamic Cooperation made the decision in an emergency meeting at the body's headquarters in Saudi Arabia and said it would "urgently dispatch" its high-level mission to the country to visit the capital to explore the situation, express solidarity with Muslims and to contribute to any peace talks.

"It has become imperative for a collective and timely engagement of the entire international community to help the new authorities restore order and stabilize the country because of the implications of the crisis on the peace, security and stability of the wider region and even beyond," said O.I.C. Secretary-General Iyad Ameen Madani.

Guinea's Foreign Minister, Lounceny Fall, will head the organization's delegation.

The body of 57 Muslim-majority member states also called on member states and others to step up aid to people in need.

The U.N. refugee agency says it will airlift aid in the coming week that will cater to 20,000 people.

Associated Press reporter Aya Batrawy in Dubai, United Arab Emirates contributed to this report.