Troops conducted house-to-house searches for several hours in a neighbourhood of Bangui believed to be a base for attacks against Muslims.
Automatic weapons, grenades, knives and ammunition were confiscated.
More than 250 military personnel were deployed in the disarmament drive.
Source: Index Mundi
The peacekeepers hope to secure the northern district of Boy Rabe.
It is a base for the anti-balaka militia - formed in response to killings by Muslim rebels and now blamed for their own revenge attacks.
The operation was not entirely successful. Some of the militia refused to disarm and one of its top leaders, Patrice Edouard Ngaissona, escaped capture.
The city's chief prosecutor said Mr Ngaissona was "the big fish who had to be detained", according to AFP news agency.
France is deploying a further 400 troops from Chad and Gabon, after French defence minister Jean-Yves le Drian admitted Paris had underestimated the level of violence and hatred in the Central African Republic.
That raises the total troop deployment of CAR's former colonial power, to 2,000.
The French military, which has been in the country since December, is working alongside 5,500 troops from other African countries.
The United Nations refugee agency has described the situation as "a humanitarian catastrophe of unspeakable proportions".
The UN's World Food Programme says that about 1.3 million people - a quarter of the population - are in need of aid.
Tens of thousands of Muslims have fled as Christian militias have stepped up their attacks in recent weeks.
The militias claim to be taking revenge for atrocities committed by Muslim rebels last year.
They accuse their victims of supporting the Muslim rebel group that seized power in March 2013, but which was forced out last month.
Many Muslims have crossed the borders into neighbouring Cameroon and Chad, while thousands more are living in camps inside CAR.
CAR is rich in gold, diamonds and other natural resources but decades of unrest and mismanagement have left most of its people stuck in poverty.
French and African peacekeepers have seized weapons from militia in the capital of the Central African Republic, which has been gripped by sectarian strife.