A number of injuries were reported and a man detained at the scene after a stabbing incident at a premises near the iconic London Bridge on Friday as police treated the attack as "terror-related".
The area, which is in the heart of British capital, remains cordoned off with heavy police and emergency services being pressed after the incident.
Details of the incident are yet to be confirmed but some eyewitnesses reported seeing a man being shot by security services.
The Metropolitan Police said the circumstances surrounding the incident remained unclear but it was treating it as "terror-related" as a "precaution".
London Ambulance Service has declared it a major incident.
Police were called at 1:58pm to a stabbing at premises near to London Bridge. Emergency services attended, including officers from the Met and City of London Police, a Metropolitan Police statement said.
A man has been detained by police. We believe a number of people have been injured, the statement said.
Images appearing on social media appear to show an exchange with the potential suspect being detained by police officers.
There are also some videos showing people running across the bridge in panic.
The transport on London Bridge remains at a standstill and offices and buildings in the vicinity are under lockdown as the incident continues to unfold.
UK Prime Minister Boris Johnson said, "I'm being kept updated on the incident at London Bridge and want to thank the police and all emergency services for their immediate response."
Home Secretary Priti Patel said she was "very concerned" over the incident.
"Very concerned by ongoing incident at London Bridge. My thoughts are with all affected. I am grateful for the rapid response of our police and I urge everyone to follow their advice," the Indian-origin minister tweeted.
London Bridge was one of the areas targeted by an ISIS-claimed terrorist attack in June 2017, when 11 people died as terrorists went on a stabbing spree after ramming a van into pedestrians.
The UK had earlier this month downgraded its terror threat level from "severe" to "substantial", which means a terrorist threat is likely rather than highly likely in the country.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)