A 27-year-old man was bitten by a police dog as four people were arrested over an alleged terror plot.
The suspect, along with a 17-year-old boy and a 31-year-old man, were held in east London – while a 32-year-old man was arrested in Leicestershire.
Police said no shots were fired during armed raids on two addresses in the capital, but the 27-year-old man was bitten on the foot by a police dog.
He was taken to hospital, where his injuries are not believed to be serious.
All four suspects were arrested on suspicion of being concerned in the commission, preparation or instigation of acts of terrorism under section 41 of the Terrorism Act (Tact) 2000.
They are being held in police custody, while police search the three addresses and another property in east London.
The Metropolitan Police said the arrests were made by counter-terror officers from London and the East Midlands as part of a “proactive investigation”.
Footage posted on social media showed at least two raids by armed police in Goodmayes, east London.
The Met’s Redbridge Borough Twitter account said the police activity in the area was related to the terror arrests.
In one video, loud bangs were clearly audible as officers near a block of flats shouted urging people to “stay inside”.
Armed police and later forensic teams could then be seen outside the block.
In what is believed to be a separate raid nearby, armed officers were seen at the front door of a house with one officer telling those inside to “walk towards me slowly” and “place your hands on your head”.
A man was then filmed leaving the house with his arms raised and was swiftly held against the front of the property by officers before being led down the street.