The arrests are said to have taken place at two addresses in Essex, northeast of the capital, on Thursday morning.
This happens at the same time as the President of the USA, Donald Trump, is visiting. He has meetings with Prime Minister Keir Starmer in Buckinghamshire, on the other side of London, during the day.
After house searches were carried out, the suspects were released on bail, according to the anti-terror spokesperson Dominic Murphy. He suggests that the three suspects are Britons who have been recruited by Russia.
Everyone who may be contacted and tempted to perform criminal acts on behalf of another country here in the United Kingdom should think twice, he says according to BBC.
The consequences for those who are convicted can be very severe.
