David Cameron and Foreign Secretary William Hague have sent messages of support to the Belgian government following an armed attack at Brussels' Jewish Museum.
The Prime Minister's Office wrote on Twitter:
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The signs were encouraging to commuters going about the transport network the day after a terror attack in Westminster.
Faith leaders from across London say religious communities will "stand together" in the wake of the Westminster terror attack.
Pc Keith Palmer was among the three people killed yesterday in the Westminster terror attack.