Three people have been taken to hospital after stabbings at two health centres in east London, police said.
A man was detained nearby and taken to hospital for treatment.
It is understood two people were stabbed in the Tredegar Practice (pictured) on St Stephen's Road, Tower Hamlets and a further person was stabbed in St Stephen's Health Centre off nearby William Place.
None of the injuries are thought to be life-threatening.
The force said the incident, which happened at around 11am, was not terror-related.
Farhad Alom, 25, who witnessed the attacks, said the assailants appeared to be Chinese men.
According to Mr Alom, a bystander at St Stephen's could not get to safety as he was in a wheelchair.
One person was stabbed in the neck and another in the stomach, he added, in what appeared to be targeted assaults.
One woman, who did not want to be named, said she saw the knife attack at Tredegar Practice and a man stepped in to stop the attacker.
The woman said she hid in a side room after witnessing "the entire event".
A man who was in the area at the time of the attack said: "A man has come out [of the surgery] quite quick so I've asked him what's wrong and he said there's a man in there that's walked into the surgery and apparently stabbed an older lady.
"Then an ambulance and couple of CID cars and armed police was here quite quick."
The man, who does not wish to be named, was at the dental surgery next door.
He added that the attack did not shock him, saying: "I don't want to say it was frightening as we're getting used to this happening in London.
"So it's frightening, but it's real."
Copyright (c) Press Association Ltd. 2018, All Rights Reserved. Picture (c) Dominic Lipinski / PA Wire.