Almost 40 Nigerian opposition parties have agreed to field a joint candidate to prevent the re-election of President Muhammadu Buhari next year.
The alliance includes the main opposition party, the People’s Democratic Party (PDP), and a splinter group that broke away from Mr Buhari’s governing All Progressives Congress (APC) last week.
President Buhari, who came to power in 2015, announced in April that he was seeking his party’s approval for running for another term in office.
The BBC’s Ishaq Khalid in the capital, Abuja, says this is one the biggest political developments in the run-up to elections in February.
The new coalition says their aim is to defeat the 75-year-old incumbent, whose first term has been beset by poor health, and rescue Nigeria from what they called ”darkness”.
Many serving senators, members of the lower house of parliament and some state governors are believed to be behind the new movement, our reporter says.
Mr Buhari has come in for criticism for his handling of Nigeria’s economy, the largest in Africa.
His administration has pointed to the fight against corruption and the military operations against Islamist militant group Boko Haram as some of his achievements.