Several people were stabbed in the southern English town of Reading on Saturday, media reports said, and police said they were investigating reports of an incident.
Sky News said the stabbings took place at the site of Black Lives Matter protest in the town earlier in the day.
Video footage posted on Twitter showed paramedics rushing to help at least three people who were bleeding on the ground in a park. Reuters was unable to verify the footage independently.
Britain's interior minister Priti Patel said he was deeply concerned to hear reports of the incident.
The head of the local council authority in Reading, Jason Brock, said police were dealing with a "serious incident" and he urged people to stay away from the town centre.
The National Police Chiefs' Council, representing senior police officers, urged people on Twitter to avoid speculation or sharing of video or images of the incident.