Scotland Yard have arrested four suspected Islamist terrorists in London on suspicion of plotting a "potentially very serious" terror attack.
The men, whose identities are not yet known, are being questioned at a south London police station on suspicion of the commission, preparation or instigation of acts of terrorism.
They had been monitored by counter-terrorism police and MI5 spies for some time and the arrests were part of a pre-planned operation.
Scotland Yard armed officers arrested the suspected Islamist terrorists in simultaneous raids across three separate areas of London last evening to foil the alleged terror plot.
The arrests were made in Whitechapel, Bayswater and Peckham areas of the city and searches under the Terrorism Act 2000 are continuing at six addresses and on two vehicles.
The Metropolitan Police's counter-terrorism officers believe the alleged plot was "potentially very serious" but did not appear to be on the scale of earlier major plots.
Two men, both aged 25, were arrested in a car in Whitechapel, east London, after police fired "Hatton rounds" -- ammunition designed to blow out tyres and blow open doors with minimal collateral damage.
A 28-year-old man was arrested at Westbourne Grove in west London, and the fourth man, aged 29, was arrested in Peckham Hill Street in south-east London.
George Paul, a businessman who witnessed the west London arrest, said it had been "very dramatic, like the movies".
"What I saw was three policeman holding an individual down while he was shouting 'please don't break my arms' or something of that ilk," he told BBC News.
The deployment of Scotland Yard's Firearms Unit raises the prospect that the Met police were looking at a possible plot to target public places with guns.