Four men detained in East London operation
The four men were held on “suspicion of being concerned in the commission, preparation or instigation of acts of terrorism”, a Metropolitan Police statement read.
Police said the men -- aged 18, 24, 27 and 28 -- were all held near their addresses in East London.
Officers are also searching five residential address in the area and a business address, also in East London.
Britain’s domestic intelligence agency MI5 was thought to be part of the investigation which led to the arrests.
The U.K. has been on high alert; last month police officers shot one woman and detained six other individuals in anti-terror raids in London and Kent.
A day before, police arrested an individual carrying knives near Downing Street -- the London residence of the prime minister.
In March, Khalil Masood was killed after driving into pedestrians on Westminster Bridge, killing three people and injuring more than a dozen others before murdering a policeman outside parliament with a knife.
A fifth victim, Romanian tourist Andreea Cristea, who had fallen into the River Thames from the bridge during Masood’s rampage, later died in hospital.