The court declared that an overwhelming majority of 95% approved the vote, and turnout at just above 57%.

The new law creates an office of a vice-president, appointed by the president, and a unicameral parliament, doing away with the senate.

It also bans politicians with dual citizenship from running for president and increases the number of supreme court judges from nine to 11.

The top court had last September scrapped the committee tasked with drafting the new law before the court's president, Daniele Darlan, was forcibly retired.

The country's main opposition parties and civil society groups had urged a boycott, saying the amended law was designed to keep President Faustin-Archange Touadéra in power for life.

They accused the constitutional review committee of taking instructions from Russia.

President Touadéra is backed by Russian Wagner mercenaries. Extra fighters had arrived ahead of the referendum to provide security.

The diamond and gold-rich landlocked country has been stricken by conflict and political turmoil for most of its history since independence from France in 1960.