Several people have been killed in a stampede at a rally in support of Nigerian President Muhammadu Buhari's candidacy days before the country's presidential and legislative elections, his office has said.
The incident on Tuesday took place in Port Harcourt, a southern city in the Niger Delta oil-production heartland.
Buhari's office said in a statement the president had been "informed of the tragic deaths of several members of his All Progressives Congress (APC) party".
Local media said panic broke out at the end of the gathering, held inside the Adokiye Amiesimaka Stadium when crowds tried to force their way through a locked exit.
"Those from behind were pushing and putting pressure on those in front leading to some persons falling on the ground and being trampled upon," said journalist Egufe Yafugborhi of the Vanguard newspaper.
In a statement, Judith Amaechi, who runs the party's regional women and youth team, expressed "deep shock over the death of APC members who were in a stampede".
The statement did not specify the number of people killed.
Separately, a spokesman for the University of Port Harcourt Teaching Hospital said the stampede claimed at least 14 lives.
"There are others under medical attention at the Emergency Unit, so we can't force a clear figure beyond what the situation is at the moment," Kem Daniel-Elebiga told AFP news agency.
The February 16 elections in Africa's most populous country will see Buhari stand for a second four-year term against former Vice President Atiku Abubakar in what is expected to be a close race.
In recent weeks, tensions have risen between the APC and Abubakar's People's Democratic Party (PDP).
The PDP has accused the government of seeking to rig the vote while the APC has said the opposition party is fomenting unrest.
On Sunday, five APC members were shot and killed near the oil hub of Warri city in southeast Nigeria, with authorities calling it a revenge attack by people suspected to be from the opposition.
Clashes between APC and PDP supporters have been reported from various places in Africa's largest democracy.
Nigeria has a history of election violence, with analysts warning that the forthcoming vote might be one of the bloodiest in its history.
The last election in 2015 was considered free and fair, but state and local elections, as well as earlier presidential polls, have been marred by violence and fraud allegations.