ABUJA, Sept 6 (Reuters) - Nigeria's presidential election tribunal is due to rule on Wednesday on whether Bola Tinubu should stay as president after two rivals challenged his victory in February's disputed vote.

       There have been numerous legal challenges to the outcome of previous Nigerian presidential elections but none have succeeded. Most political observers expect the tribunal to uphold Tinubu's win.

       Atiku Abubakar of the People's Democratic Party and Labour Party's Peter Obi asked the court to invalidate the election, alleging irregularities and accused the electoral body of breaching the law by failing to use electronic machines to upload polling station results, among other criticisms.

       The tribunal, which will deliver its ruling in the capital Abuja, has the power to cancel an election and order a fresh one, among other remedies.

       If it upholds Tinubu's win, Atiku and Obi can still make a final appeal at the country's Supreme Court, the highest court in Nigeria. An appeal should be concluded within 60 days from the date of the tribunal judgment.

       Ahead of the ruling, the military set up check-points on major roads into Abuja, randomly searching commuters and vehicles.

       Tinubu, who is in India ahead of a G20 Summit, has defended his victory and says he is focused on reviving the economy. He has implemented reforms that include removing a popular but costly petrol subsidy and ending currency controls.

       But getting Nigerians to stomach the painful reforms has been hard and the 71-year-old veteran faces opposition from labour unions, who started a two-day strike on Tuesday ahead of an indefinite strike from Sept. 21.

       Anaemic growth, high unemployment, the highest inflation rate in two decades, record debt, massive oil theft that has hit government revenues and widespread insecurity are among the issues that Tinubu inherited from predecessor Muhammadu Buhari.

       Fixing these pressing problems requires public support but Tinubu garnered 8.79 million votes, the fewest won by a Nigerian president since the country returned to democracy in 1999, limiting the goodwill towards him.

       Writing by MacDonald Dzirutwe; Editing by Alison Williams

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