One of the defeated opposition candidates in Nigeria's presidential election has formally challenged the results in a petition filed at a court tribunal in the capital, Abuja.

Peter Obi of the Labour Party came third in last month's poll behind Atiku Abubakar and victor Bola Tinubu of the All Progressives Congress.

A spokesperson for Mr Obi's presidential campaign told the BBC on Tuesday that their petition argues that Mr Tinubu should not have been eligible to run for the top office.

It also raises questions on the processes leading to the outcome of the election and the announcement of a winner by the Independent National Electoral Commission, he added.

Mr Abubakar, the who ran for president with the Peoples Democratic Party, has also vowed to challenge the election results.

Election disputes take months to be resolved in Nigeria, despite the constitution stipulating that they should be concluded, where possible, before a candidate is sworn into office.

This year's election was the tightest presidential race since the end of military rule in 1999, but international observers said it lacked transparency and there were operational failures.

The electoral commission has acknowledged that there were major technical hitches which affected the uploading of election results on its server.