LAGOS - Bola Tinubu will be sworn in as Nigeria's president on Monday under the cloud of a disputed election and pressure to quickly improve economic and security conditions, which many complain worsened under his predecessor Muhammadu Buhari.

Two of Tinubu's main opponents in the February election are challenging his victory on the basis of fraud claims, and a tribunal will on Tuesday start hearing their main arguments. A ruling is not expected before September.

Buhari, a taciturn former military ruler, leaves Africa's biggest economy and most populous nation deeply divided.

The election had galvanised young voters hoping for a break from the two parties that have dominated Nigerian politics since military rule ended in 1999. But what authorities promised would be the country's freest and fairest election yet ended in frustration for many.

Tinubu, a member of Buhari's All Progressives Congress who has long exerted influence from behind the scenes, won with 37% of the vote, the lowest share since 1999.

BUHARI'S RECORD

He inherits a struggling economy with record debt, shortages of foreign exchange and fuel, a weak naira currency, near two-decades-high inflation, skeletal power supplies and falling oil production due to crude theft and underinvestment. A raft of protectionist economic policies and foreign currency interventions have also spooked investors.

Buhari defends his record, saying new infrastructure such as roads, bridges and airports, and the protectionist policies have laid the foundations for future growth.

He has also touted successes in a 13-year fight against Islamist insurgents in the northeast, where his government ramped up military spending.

But insecurity has spread, leaving many Nigerians feeling more unsafe. Killings and kidnappings for ransom are rampant in the northwest. Separatist and gang violence plague the southeast, and clashes between farmers and herders persist in hinterland states known as Nigeria's Middle Belt.

A former Lagos state governor, Tinubu has promised to be a better steward of the economy.

Opponents are sceptical: They see him as part of an old guard that held back Nigeria and an entitled political "godfather" who said last year that it was his turn to leadafter backing Buhari for the top job in 2015.

  - Reuters