Three women and a man were fatally stabbed Monday morning in the London Borough of Southwark, police said.
A suspect described as a man in his late 20s was arrested and is in custody, police added.
Police say they think the attacker and the victims knew each other. The female victims were in their mid-60s, 40s and 30s, and the man in their mid-60s, police said.
No information was immediately available about the circumstances surrounding the murders.
“This is a terrible incident and I fully understand how concerned the community will be,” Colin Wingrove, the Metropolitan Police Superintendent, said in a statement. “We’re working closely with our partners and local community groups to keep everyone informed and answer their questions.”
Officers responded to reports of a disturbance on Delaford Road in Southwark at 1:40 am. After forcing entry, they found four people with what appeared to be stab wounds, police said.
The four people were pronounced dead at the scene, police added.
Although murders are less common in Britain than in the United States, security and policing remain major problems in London. According to police statistics, there were 103 murders in the city in 2021, 71 of which involved knives or sharp instruments.