A stampede in Nigeria's Port Harcourt killed at least 31 people and injured several others, officials said on Saturday.

The crowd was waiting for the start of a charity event where food and presents were to be distributed.

Initial reports indicated that the tragedy took place at a local Pentecostal church. However, local news outlet Punch reported that the church leaders actually organized the annual "Shop for Free" charity program at the Port Harcourt Polo Club because it had more room. Some citizens apparently started waiting in line as early as Friday for the event that was due to start at 9 a.m. local time on Saturday.

"People were there earlier and some got impatient and started rushing, which led to stampeding," said police spokesperson Grace Iringe-Koko.

Eventually, the crowd broke through the church gate and some of the people at the scene were trampled.

Church members had been seated inside when the stampede started, senior emergency management official Godwin Tepikor told the AFP news agency.

"A huge crowd from outside surged into the club through a narrow gate, resulting in the stampede," he said.

"The police are on the ground monitoring," according to Iringe-koko.

Children said to be among the victims

A witness told the AP news agency that "there were so many children" among the dead, and that a pregnant woman also lost her life. Some members of the church which organized the event were reportedly attacked by relatives of the victims following the stampede.

Security forces have cordoned off the area after the incident. Police said a criminal probe has been launched. 

Nigeria has seen several deadly stampedes in recent years, including one last year in the northern state of Borno, which claimed seven lives. At least 15 people were killed in a stampede at an election rally for Nigerian President Muhammadu Buhari in 2019.

But tensions have been higher than normal in recent months, with the Ukraine crisis driving up the cost of food and fuel and aid agencies warning about a possible food insecurity crisis in Africa.

dj/msh (Reuters, AFP, dpa)