A judge in Central African Republic has asked parliament to lift the immunity of four opposition lawmakers as part of an investigation into ex-president Francois Bozize, the interim justice minister said on Thursday.

The authorities and United Nations accuse Bozize, who was forced out in a 2013 rebellion, of backing rebels who violently disrupted December's presidential election and sought to seize power.

Lawmakers Anicet Georges Dologuele, Martin Ziguele, Karim Meckassoua and Simplice Zingas, who have already been barred from travelling abroad, are of interest to the judge investigating Bozize's case, minister Arnaud Djoubaye Abazene told Reuters without giving further details.

Dologuele and Ziguele are former prime ministers, who came second and third respectively in the December 27 presidential vote. Pursuing legal proceedings against them could worsen political divisions laid bare by the turbulent election and its aftermath.

The four declined to comment until parliament decides whether to lift their immunity.

President Faustin-Archange Touadera was sworn in for a second five-year term in March despite the opposition's call for a re-run of the election over alleged irregularities and low turnout.

He has promised to launch a national dialogue aimed at easing political tensions and crack down on rebel groups who have stoked instability since the 2013 rebellion ousted Bozize.

Violence has subsided in the last two months and the army has retaken several towns from militants who had occupied them since December, but insecurity remains widespread. Some 25% of the country's 5-million population is displaced.