The murder of a Muslim man sparked reprisal attacks on a Christian neighborhood over the weekend. UN peacekeepers were forced to fire warning shots to disperse thousands of protesters who were calling for an increased role for the nation's army.
The majority Christian country has been plagued by violence since March last year, when largely Muslim Seleka rebels ousted the president. The violence has killed thousands and displaced nearly a million people.
Members of a Christian militia known as the anti-Balaka attacked the prison on Monday, freeing hundreds of soldiers and militiamen.
The Seleka rebels relinquished power in January. A transitional government, led by interim President Catherine Samba-Panza, has been given the task of organizing elections no later than early next year - but there are doubts this can happen, given the ongoing violence.
Since the latest upturn in violence began at the weekend, more than 30 people have been killed.
The United Nations children's agency, Unicef, said at least three teenagers had been killed, with one beheaded.
Prisoners escaped from the Ngaragba jail in the capital Bangui on Monday evening. "There is no-one in the prison," Reuters news agency quoted a senior security source as saying.
Thousands of protesters marched on the presidential palace on Monday to call for greater power for the army, which has seen its powers reduced since an interim government was installed in January 2014.
Interim President Catherine Samba Panza has cut short her trip to the UN General Assembly.
Presidential elections are scheduled for October, a month before Pope Francis visits Bangui.
