Chad's prime minister and opposition leader Succes Masra has tendered his resignation after interim President Mahamat Idriss Deby was confirmed as a winner of the May 6 presidential election, Masra said on Wednesday.

Masra, a staunch opponent of the junta, which seized power in April 2021, was appointed prime minister of the transitional government in January, four months ahead of the poll, in a move to appease the opposition.

In March, his candidacy was cleared for the presidential election to return the country to constitutional rule. The oil-producing country is the first of a string of coup-hit states in West and Central Africa's Sahel region to attempt such a return.

Before the official announcement of preliminary results Masra claimed victory, alleging that electoral fraud was being planned.

Chad's state election body said Deby had won the election outright with 61 percent of the vote and the constitutional council later confirmed him as a winner.

Masra has acknowledged the council's ruling and said there were no other legal means to contest the results.

"In accordance with the constitution, I have today presented... my resignation and that of the transitional government, which has become irrelevant with the end of the presidential election of May 6," Masra said on X on Wednesday.

Deby's victory prolongs the rule of the family that has had a firm grip on power since his father took over in a coup in the early 1990s.