'We are not afraid' message circulated online
Britons have begun sharing the picture online – telling the killers the country does not fear them.
The movement has begun on social media after an attack on Westminster Bridge and inside Parliament.
At least one person is dead after a car ploughed into pedestrians on the bridge and a police officer was stabbed.
The attacker was shot by armed police outside the Palace of Wesminster.
Witnesses have said there are bodies in the Thames River.
London Terror Attack: LIVE IMAGES Wed, March 22, 2017
Two dead in Parliament shooting as 12 mown down in Westminster
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Emergency services at the scene outside the Palace of Westminster, London, after policeman has been stabbed and his apparent attacker shot by officers in a major security incident at the Houses of Parliament
One person posted the meme and wrote: “My heart is saddened by the loss of the person that died in this terrible day of terror #we are not afraid”
Another said: “We are not save (sic) anymore. Nowhere. But still, we are NOT afraid. We do NOT let this scare us. #PrayForLondon”
— Corey Smith UKIP (@coreysmithukip) March 22, 2017
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Pedestrians were hit by a car on Westminster Bridge
The image has the phrase written on a Tube sign.
However, the message has been criticised already, with people suggesting it is offensive to the families of victims.