ABUJA, Nigeria (AP) — A court in Nigeria has been asked to stop the planned inauguration of the country’s next president and to extend the incumbent's tenure, court documents obtained Friday show.

Five Nigerians made the request to the Federal High Court in Abuja, arguing that President-elect Bola Tinubu was illegally declared the winner of the Feb. 25 presidential election and therefore should not be sworn into office on May 29.

The petition is among several challenges to the ruling party’s victory and raised concerns in the West African nation about a possible constitutional crisis should President Muhammadu Buhari remain in office until the case is decided.

Chuks Nwachuku, the plaintiffs' lawyer, said Tinubu's being declared president-elect was unconstitutional because he failed to win at least 25% of the votes cast in Abuja, Nigeria's capital city.

To be elected president, the Nigerian Constitution requires a candidate to win both the highest number of votes overall and not less than one-quarter of the votes in each of at least two-thirds of the country's 36 states and Abuja.

The interpretation of that constitutional provision has remained a subject of debate in Nigeria.

"There can be no swearing in of anyone who has not satisfied the provisions of the constitution. We are asking for a declaration that the president remains in office until the issue of succession is sorted out,” Nwachuku told The Associated Press.

Nigeria’s two main opposition parties previously contested the All Progressives Congress party’s presidential victory, alleging the election results were rigged.

While the opposition's election challenge was not expected to stop Tinubu's inauguration, analysts warned that extending Buhari's tenure could create a crisis for a country with a checkered history of long military rule and electoral violence.

“The petition is a recipe for crisis. All the previous elections were disputed, but at no point in time did anybody push that the constitutional provision of inaugurating the winner should be stopped, so it is very worrying,” Idayat Hassan, who leads the Center for Democracy and Development, a research and advocacy organization based in Abuja.