There was no immediate comment from authorities in the town of Buea in South-West Region, where 529 athletes were running up the highest mountain in west and central Africa as they competed in the Mount Cameroon Race of Hope.
The armed wing of Ambazonia Governing Council, one of the separatist militia groups, claimed responsibility for the blasts.
"Our primary target was the Cameroon elite forces... that were providing security for the athletes. We will not allow Cameroon to continue its occupation," the group's spokesman Capo Daniel told Reuters.
A video shared widely on social media that Reuters was not immediately able to verify showed spectators cheering on a runner before dashing for cover when a small explosion goes off in the distance.Â
Another video showed a different explosion going off near a pack of runners elsewhere on the route.
"Nineteen athletes have been brought to our facility with injuries. We have operated upon three of them. Their condition is stable and we haven't recorded any deaths," Martin Mokake, the director of Buea Regional Hospital, told Reuters by phone.
One of those being treated was a Gabonese citizen, he said.
Participants in the race included athletes from east, central and northern Africa and France.
The separatist insurgency began in Cameroon's English-speaking North-West and South-West regions in 2016 when teachers and lawyers protested against their perceived marginalisation by the primarily French-speaking central government.
A violent crackdown by security forces helped radicalise the movement, and the ensuing conflict has killed more than 3000 people and displaced nearly one million.
