Several people were injured in a scuffle between police officers and motorcycling enthusiasts in Athi River, Machakos County on Sunday.
The "Riders Covid-19 virus vaccination drive" was to see more than 100 riders and fans vaccinated against the deadly virus.
Dozens of riders under Raceline Events Limited converged for the racing competition as early as 7am but a contingent of armed police officers from Athi River police station, led by the deputy commander, arrived and disrupted the occasion.
The event organisers, armed with a court order permitting the event, tried in vain to reason with the police officers.
It was alleged that an unnamed senior officer in the Sports ministry ordered the cancellation of the event, citing the need to adhere to anti-virus protocols, after he was stopped from participating in it.
This prompted the organiser to take the matter to the Milimani Commercial Court on September 24, and obtain the order allowing the event to take place.
But the police officers disrupted it on Sunday, firing live bullets in the air and hurling teargas canisters at participants.
The venue - the Whistling Moran private racing grounds - turned chaotic, with participants scampering for safety.
Several people including women and children were injured while vehicles and motorcycles were damaged.
The vaccination drive was paralysed with food vendors counting heavy losses.
"I came to the race hoping to get a Covid 19 jab. Everyone allowed into the venue had a temperature check and all Covid-19 protocols were observed. The event was by invitation to control the crowd. It's unfortunate it had to end this way," said Allan Muigai, a participant.
Raceline Events’ spokesperson, Mr Kennedy Marete, claimed individuals in the Sports ministry used police officers to disrupt the event after their attendance was prevented.
"Our members were injured after a police officer fired in the air and hurled teargas canisters, resulting in a stampede. The irony is that police officers can ignore a court order and use Covid-19 protocols to stop an event. It's barbaric and unethical," said Mr Marete, an advocate of the High Court.
The police officers retreated after the melee but surrounded the racing field to prevent any activities.
The Whistling Moran racing ground has been hosting car and motorcycle races every weekend under strict adherence to Covid-19 protocols.