Central African Republic President Faustin Archange Touadera is on track to win last weekend's elections, his party said on Thursday, a day after the opposition called for the vote to be annulled.

"Trends... point to a first-round victory by Professor Touadera, reflecting the renewed legitimacy that the people have conferred on our candidate," his campaign director, Simplice Mathieu Sarandji, told a news conference.

A powerful coalition of opposition groups said Wednesday the vote in the violence-torn country had been badly flawed, and called for its "cancellation, pure and simple."

Sarandji said the electoral and judicial bodies could be trusted.

"No candidate has any right to go through non-official channels to call for the elections to be cancelled and to be held again," he said, speaking at the headquarters of Touadera's United Hearts Movement (MCU) party.

The elections, staged last Sunday for the presidency and the legislature, are widely seen as a key stability test for the CAR.

The landlocked country is one of the poorest in the world and among the most volatile, suffering a string of coups and wars since gaining independence from France in 1960.