Three people have been stabbed at a GP surgery in Tower Hamlets.
A man has been arrested after the attack at St Stephen's Health Centre on Wednesday morning, police said.
Armed police raced to the medical practice in St Stephen's Road after three victims were stabbed shortly after 11am.
All three have been taken to hospital, Scotland Yard said.
Two people were stabbed in St Stephen's Road while a further person was stabbed at St Stephen's Health Centre.
Farhad Alom, 25, who witnessed the attacks, said 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.
A man who was in the area at the time of the attack said: "A man has come out 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 woman said she hid in a side room after witnessing "the entire event".
A Scotland Yard spokesperson said: "We await an update on their condition," a spokesman said.
"A man was detained nearby and taken to hospital suffering from an injury."
"Cordons remain in place while enquiries are ongoing."
Police have confirmed that the incident is not terror related.
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