Chadian opposition leader Succes Masra has lodged a legal appeal with the country's constitutional council to challenge the preliminary result of the Central African nation's May 6 presidential election.

The state-run national election management body on Thursday declared interim President Mahamat Idriss Deby winner of the election with 61.3% of the vote, according to provisional results, while Masra was placed a distant second with 18.53%.

However, prior to the official announcement, Masra, who serves as the prime minister of a transitional government, had claimed victory, alleging that an electoral fraud was being planned.

"With the help of our lawyers, ... we submitted a request to the Constitutional Council to reveal the truth of the ballot boxes," Masra said in posts on social media platforms Facebook and X on Sunday, urging his supporters to remain calm.

He shared a copy of a receipt showing that documents had been filed with the council, which an opposition official close to Masra said included copies of results sheets from polling stations, a table pulling together the figures and videos that allegedly show ballot stuffing and other cheating.

"We documented everything," the person said.

Political tensions are running high in Chad, the first of a string of coup-hit countries in West and Central Africa to attempt a return to constitutional rule. Deby seized power in April 2021 when rebels killed his long-ruling father, Idriss Deby.

At least 10 people, including children, were killed and dozens were injured by celebratory gunfire on Friday following the announcement of the results, according to Amnesty International and Chadian media.

Chad's health ministry confirmed that a number of people were hurt during the celebration of Deby's win, but asked journalists not to film or report on patients inside hospitals, a move condemned by Chad's press unions.