President Faustin-Archange Touadéra announced the lockdown between 8pm and 5am in a statement read out on national radio on Thursday night.
Touadéra, 63, won five more years in power following presidential and parliamentary elections on 27 December.
However, fighting has continued in towns nationwide since the election, with the rebels threatening to march on the capital, Bangui.
According to Minusca, the UN peacekeeping force in the country, rebel advances have faltered over the last 10 days with the exception of Bangassou, 750km east of the capital Bangui.
Three court appeals
Touadéra was declared winner in the first round by the electoral authorities with 53.92% of the vote.
On Thursday three appeals were filed at the court challenging the result. Two were in the name of opposition candidates Martin Ziguélé and Anicet Georges Dologuelé. A third was lodged on behalf of 10 candidates.
All of them denounce what they consider to be irregularities such as the disappearance of ballot papers, intimidation and vote buying.
Arlette Sombo Dibele, who filed the petition for the 10 candidates, said: “The candidates have many complaints. There were massive and obvious violations of provisions of the electoral code.”
“They also deplore the fact that half of the country's voters were unable to vote,” said Bernard Dillah, campaign director of Ziguélé's MLPC party.
“Not all Central Africans were able to vote. More than half could not vote. But the constitution tells us that the presidential election is a universal election. That means that all Central Africans must vote. This is already an irregularity.”
The constitutional court has until 19 January to validate the election result.
