A mass stabbing that killed three and injured others at a suburban London park is being treated as a terrorist attack, British police announced Sunday.

Deputy Assistant Commissioner Dean Haydon, Britain’s national coordinator for counterterrorism policing, has determined the Saturday night attack in the town of Reading was a terrorist incident, and Thames Valley Police are turning over the case to counterterrorism investigators, officials said.

A 25-year-old man arrested at the scene is believed to be the lone perpetrator, police said. The suspect is a Libyan national who sought asylum in Britain, according to multiple reports in British media.