Four men have been arrested over an alleged terrorist plot after police carried out raids across London and blew out the tyres of a car carrying two of the suspects.

A group of men, who were said to have had access to an arms cache, had been under surveillance by police and MI5 for some time following intelligence reports that they were planning to carry out an attack.

The focus of the plot was said to be on the capital and, although serious, was not, it is believed, at the highest end of those the intelligence and security services have had to deal with in recent times. They denied reports that it involved a “Nairobi-style” assault.

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The two men dragged out of the car after the use of “Hatton Rounds” – large shotgun ammunition used to stop vehicles and blow the hinges off doors – by officers in Mansell Street, Whitechapel, east London were British nationals of Turkish and Algerian descent. Two other UK citizens, of Azerbaijani and Pakistani origin, aged were held respectively at Westbourne Grove, Bayswater and Peckham, south-east London.

The Westbourne Grove arrest was carried out as a man left an Iranian restaurant, the Alounak. George Paul, 30, who saw the incident, said: “The man was shouting something like, ‘Please don’t break my arms, please don’t hurt me.’ He was cuffed-up and pushed up against the front of the restaurant. There was a lot of shouting from people, but some of them might have been passers-by.”

City of London council member John Fletcher, who lives near Whitechapel’s Mansell Street, said he initially heard two loud bangs which he believed to be fireworks and went to investigate. Neighbour Catherine Delgado, 43, who saw the incident, said “five or six” cars surrounded one vehicle, blocking off the street.