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% 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 Deby's father took over in a coup in the early 1990s.