World leaders have offered their support to London and expressed condolences to the victims in the attack that left seven dead and at least 48 others injured on Saturday night.
Prime Minister Theresa May, who is expected to chair an emergency Cobra meeting on Sunday, said in a statement: "I want to express my huge gratitude to the police and emergency services who are on the scene. Our thoughts are with those who are caught up in these dreadful events."
Here's how international leaders have been voicing their solidarity.
President Donald Trump led the messages of sympathy, but first, he responded to the attack by arguing in favour of his controversial travel ban.
One tweet read: "We need to be smart, vigilant and tough. We need the courts to give us back our rights. We need the Travel Ban as an extra level of safety!"
A few minutes later, Trump tweeted a message of support for Londoners: "Whatever the United States can do to help out in London and the U. K., we will be there - WE ARE WITH YOU. GOD BLESS!"
Heather Nauert, spokesman for the US Department of State, said the President had offered condolences to the Prime Minister on Saturday evening. In a statement, she said: "The United States stands ready to provide any assistance authorities in the United Kingdom may request.
"Our hearts are with the families and loved ones of the victims. We wish a full and quick recovery to those injured in the attacks.
"All Americans stand in solidarity with the people of the United Kingdom."
Malcolm Turnbull, the Prime Minister, said: "Our prayers and resolute solidarity are today as always with the people of Britain in the face of the shocking terrorist attacks in London."
Justin Trudeau, Canada's Prime Minister tweeted: "Awful news from London tonight. We're monitoring the situation."
French President Emmanuel Macron said French citizens were among those injured in the London attack.
In a statement denouncing the "abominable and cowardly" attack, Macron said France will continue fighting "terrorism with all our strength alongside Britain and all other countries concerned."
On Twitter, he wrote: "In the wake of this new tragedy, France more than ever stands side by side with the United Kingdom. My thoughts are with the victims and their loved ones.".
German Chancellor Angela Merkel said in a statement on Sunday that she learned with "sadness and dismay" of the attacks in the London Bridge area Saturday night.
She said that "today, we are united beyond all borders in horror and sorrow, but also in determination."
She stressed that "in the fight against every form of terrorism, we stand firmly and with determination at Britain's side."
Spanish Prime Minister Mariano Rajoy wrote on his Twitter: "I am following with great concern the attacks in London, sad news. Our solidarity and support for the British people and authorities."
Italian Premier Paolo Gentiloni tweeted: "Solidarity with the British government and a shared effort against terrorism. We are united in memory of the victims."
Philippine President Rodrigo Duterte expressed his sympathies to the victims of the attack. Duterte's spokesman Ernesto Abella said "acts such as these touched not only the people of London, they also touched all peace-loving people in the global community."
Indonesia, the world's most populous Muslim nation, also condemned the attacks and reaffirmed its support and solidarity with Britain in its efforts to combat "radicalism and terrorism."
India's Prime Minister Narendra Modi has condemned the attacks in London, saying they caused shock and anguish.
He said in a brief statement after returning from Europe that his thoughts are with the families of the deceased and offered prayers for the injured.
Celebrities have also been showing their support and sharing their condolences on social media. "Praying for London," Ariana Grande, who helped to organise Manchester attack, wrote on Twitter.
Khloe Kardashian, Ivanka Trump, Bella Thorne and Cara Delevingne also sent their prayers to the capital.
Additional reporting from Associated Press.