Five men are continuing to be questioned by police over an alleged terror plot in the UK.
The men, including four Iranian nationals, are being held over an alleged plan to "target a specific premises", the Metropolitan Police said.
They were arrested in Swindon, west London, Stockport, Rochdale and Manchester.
Three other Iranian men were arrested in London on Saturday as part of a separate counter terrorism investigation.
As part of an investigation into an alleged terror plot police arrested the men - two aged 29, a 40-year-old and another aged 46 - in the early hours of Saturday morning. The fifth person's nationality and age has not been confirmed.
Footage showed armed officers taking a man from a house in Rochdale, while another man was dragged through the street in Swindon with plastic bags over his arms.
Separately, the Met said three Iranian men - aged 39, 44 and 55 - were arrested under section 27 the National Security Act at addresses in north-west and west London, while searches continued.
The act covers offences deemed a threat to national security. Section 27 grants police the power to arrest someone without a warrant if they are reasonably suspected of being involved in "foreign power threat activity".
Cdr Dominic Murphy, head of the Met's Counter Terrorism Command, stressed that they were not linking the two investigations.
He said the operations were "certainly significant and it is unusual for us to conduct this scale of activity".
Last year MI5 said it had responded to 20 Iran-backed plots since January 2022.
Director general Sir Ken McCallum, said these presented "potentially lethal threats to British citizens and UK residents".
