Scotland Yard is reviewing plans to protect the public over the Christmas and New Year period following the attack in Berlin on Monday (December 19), which Sadiq Khan has described as a "cowardly act of terror".
The Metropolitan Police is warning Londoners that the threat level remains at "severe", meaning an attack is highly likely in the UK.
The force is considering a range of threats including the use of large vehicles and as a precaution has already started to re-evaluate its plans following the incidents in Berlin and Ankara.
The feared "terror attack" on a Berlin, Germany, Christmas market has killed at least 12 people and left 50 others wounded, after a lorry ploughed through the crowds on Monday (December 19) night.
Photos have emerged of the devastation which has struck the country with many laying down flowers and messages at the site.
In Ankara, Turkey, Russian Ambassador, Andrei Karlov, was shot dead during a speech he was giving on the same day.
Messages of condolences have poured in from politicians across west London following the attacks.
Mayor of London Sadiq Khan , has said security measures are under review and keeping people safe is the "highest priority".
In a tribute, Mr Khan said: "My thoughts and prayers are with everyone affected by the awful suspected attack on Berlin last night, particularly those who were injured, the families and friends of those who were killed and all the emergency responders.
"We don't yet have the full details, but this appears to have been a horrific and cowardly act of terror.
"All Londoners stand in solidarity with the people of Berlin today - this was an attack on our shared values, freedoms and way of life.
"I want to reassure Londoners and those visiting our city over Christmas that the Metropolitan Police will review all security plans in London in light of last night's events, and that keeping everyone safe remains the highest priority for the Met commissioner and for me."
MP for Feltham and Heston Seema Malhotra said she had been in Berlin just last week.
Ms Malhotra tweeted: "Last week I was at a festive Berlin Christmas Market.
"Cannot believe the news. We send love to all affected. Our thoughts are with you."
MP for Ealing Central and Acton, Rupa Huq said the events were "shocking".
And Boris Johnson , MP for Uxbridge and South Ruislip tweeted: "My thoughts & condolences are w/ the people of Germany following tonight's terrible tragedy in Berlin, leaving so many dead & injured."
He also wrote of his "shock" following the murder in Turkey.
A statement from the Metropolitan Police said: "The Metropolitan Police has detailed plans for protecting public events over the Christmas and New Year period.
"These already recognise that the threat level is at 'severe', meaning an attack is highly likely, and have considered a range of threats, including the use of large vehicles.
"As a matter of routine, as a precaution, we review our plans after attacks overseas, and we are doing so at present following the awful incidents in Berlin and Ankara last night."
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