The death toll has reached 15 in a stampede at an election campaign rally in southern Nigeria held by President Muhammadu Buhari, confirmed health officials on Wednesday. 

The incident happened at the Adokiye Amiesimaka, a stadium in the southern city of Port Harcourt located in the country's Niger Delta oil-production heartland when the crowd surged toward a gate after the president's speech. 

Voters in Nigeria will go to the polls on Saturday. Former vice-president Atiku Abubakar is viewed as Buhari's main challenger in the race to govern the continent's top oil-producing nation. 

In a statement, Judith Amaechi, who runs the women and youth team in support of Buhari in the region for his All Progressives Congress (APC) party, expressed "deep shock over the death of APC members who were in a stampede."

The statement, which did not specify the number of people killed, said it occurred after the rally.

Accidents sometimes occur at political rallies in Nigeria, which are often crowded. Last week, Buhari offered his condolences after supporters were killed in a stampede at a rally in the eastern state of Taraba.

(With inputs from agencies)