Four men aged between 34 and 52 were stabbed in the popular tourist hub of Covent Garden in the British capital on Wednesday, the Metropolitan Police said.
A 47-year-old woman was arrested at the scene on suspicion of possession of an offensive weapon and assault in a case the police believe is a "mental health-related" incident.
A helicopter air ambulance was seen landing at Trafalgar Square as the men, aged 34, 39, 42 and 52, were treated by paramedics before being taken to a major trauma centre by road.
"A woman has been arrested after multiple people were stabbed in Covent Garden today," the Metropolitan Police said.
"While at an early stage of the investigation, this is believed to be a mental health-related incident. Officers seized a pair of scissors at the scene," a police spokesperson added.
In a statement, the London Ambulance Service said it was called to reports of stabbings at Endell Street on Wednesday afternoon local time, where it treated four patients at the scene and "took them all to a major trauma centre as a priority by road".
Endell Street in Covent Garden lies at the heart of London's West End theatre district and was milling with crowds at the time of the stabbings.The Met Police have set up a cordon in the area while their investigations remain ongoing.