Fierce clashes between the two groups erupted after the killing of a Muslim taxi driver in Bangui on Saturday.
At least 36 people have died in the violence, and the United Nations (UN) says it has forced nearly 30,000 people to flee.
A UN spokesman said the country may be returning to a state of unseen violence since conflict erupted two years ago.
“We fear that the violence we’re seeing in Bangui is a return to the dark days of late 2013 and 2014, when thousands were killed and tens of thousands had to flee their homes,” Leo Hobbs said.
The Central African Republic has been wracked by violence since a mainly Muslim rebel group, Seleka, seized power in march 2013.
The Seleka group was then ousted, sparking a wave of violent reprisals against the Muslim population, thousands of whom fled their homes.
Interior Minister, Modibo Bachir Walidou, told BBC that the government remained in control, but the situation remained volatile.
Interim President, Catherine Samba Panza, returned from the UN General Assembly on Tuesday, telling the BBC that elections postponed for October would now be canceled.
She accused ‘former dignitaries’ of fomenting violence, singling out former President Francois Bozize.
Mr Bozize has criticised the decision to Barr him from standing for election, saying: “democracy was murdered in front of everyone in the Central African Republic.”