Leaders of countries affected by recent terror attacks have voiced solidarity with the UK after the deadly attack near the Houses of Parliament. Leaders of France and Germany, which suffered deadly vehicle attacks last year, offered the UK their support.
The US president offered condolences and praised UK security forces. The Argentine foreign ministry expressed condolences and solidarity, condemning the attacks and reiterating its determination to fight terrorism in the framework of international law.
Among the at least forty people injured by the car on Westminster Bridge are three French school children and two Romanians.
In Paris, the lights of the Eiffel Tower went out from midnight (23:00 GMT) in a tribute to the victims.
President Francois Hollande expressed his solidarity with the British people, saying terrorism concerns us all and France knows how the British people are suffering today.
July last year, a man drove a truck into pedestrians in the southern city of Nice, killing 84 people. The attack was claimed by the Islamic State (IS) group.
German Chancellor Angela Merkel, whose country saw a truck attach in December that killed 12 people in Berlin and was also claimed by IS, said her thoughts were with our British friends and all of the people of London.
I want to say for Germany and its citizens: we stand firmly and resolutely by Great Britain's side in the fight against all forms of terrorism, she added.
US President Donald Trump spoke by phone to British Prime Minister Theresa May to offer his condolences and to praise the effective response of UK security services.
Mr Trump pledged the full co-operation and support of the US government in bringing those responsible for the attack to justice, the White House said in a statement.
Saying his thoughts were with London tonight, European Commission President Jean-Claude Juncker recalled it was the first anniversary of the Brussels attacks. March 22 marks one year since the people of Brussels and Belgium suffered a similar pain and felt the support of your sympathy and solidarity, he said in a statement.
At this emotional time, we at the European Commission can only send that sympathy back twofold.
Canadian Prime Minister Justin Trudeau said in a statement that it was an attack on democracies around the world and Canadians stood united with the British people in the fight against terrorism
Australian Prime Minister Malcolm Turnbull said it was an attack on parliaments, freedom and democracy everywhere and offered his support and solidarity to the British government.
Dutch Prime Minister Mark Rutte said: Horrible images from London. The very heart of the city has been struck. Our thoughts are with the British people
Russian foreign ministry spokeswoman Maria Zakharova expressed sympathy for the injured and offered condolences to the relatives of those who had died, adding: We don't split terrorism into categories; we consider it as absolute evil. At this moment, as always, our hearts are together with the British people.
The Argentine government condemned the inhuman attack perpetrated in London and expressed its condolences and solidarity to the British government and people, the relatives of the casualties and injured, wishing them a quick recovery.
Argentina reaffirms its determination to deepen the fight against terrorism and preserve international peace and security, in the framework of international law and respect for human rights”