Britain
London Mayor Sadiq Khan said the attack was "a deliberate and cowardly attack on innocent Londoners and visitors to our city enjoying their Saturday night," adding: "There is no justification whatsoever for such barbaric acts".
Prime Minister Theresa May confirmed that the "terrible incident in London" was being treated as "a potential act of terrorism" and said she would hold emergency ministerial talks later in the day.
Opposition Labour Party leader Jeremy Corbyn: "Brutal and shocking incidents reported in London. My thoughts are with the victims and their families. Thank you to the emergency services."
Scottish Nationalist Party leader Nicola Sturgeon: "Dreadful news from London. My thoughts are with all those affected."
Far too much tolerance of extremism in Britain, says May
Australia
Prime Minister Malcolm Turnbull: "Prayers and resolute solidarity are today as always with the people of Britain in the face of the shocking terrorist attacks in London."
Germany
Chancellor Angela Merkel said she was saddened and dismayed by the attack in London on Saturday in which at least seven people were killed, and that Germany stood by Britain's side in the fight against terrorism.
"Today, we are united across all borders in horror and sadness, but equally in determination," Merkel said in a statement issued on Sunday.
"I stress for Germany: in the fight against all forms of terrorism, we stand firmly and decisively at Britain's side."
United States
US President Donald Trump said on Saturday evening Washington time: "Whatever the United States can do to help out in London and the UK, we will be there - WE ARE WITH YOU. GOD BLESS!"
Then on Sunday morning he tweeted: "At least 7 dead and 48 wounded in terror attack and Mayor of London says there is "no reason to be alarmed!"
State department called the assaults "cowardly attacks targeting innocent civilians" and added: "The United States stands ready to provide any assistance authorities in the United Kingdom may request."
US pop star Ariana Grande whose concert in Manchester last month was the scene of a deadly suicide bombing, tweeted simply: "Praying for London."
European Union
European Commission chief Jean-Claude Juncker: "Following latest London incidents with horror. Thoughts and prayers are with the victims and their families. Please stay safe."
France
President Emmanuel Macron: "In the face of this new tragedy, France is more than ever at Britain's side. My thoughts go out to the victims and their loved ones."
Canada
Prime Minister Justin Trudeau said Saturday that Canadians "stand united" with London.
"Awful news from London tonight. We're monitoring the situation," Trudeau said on Twitter.
During a reception with parliamentary press, Trudeau added: "Canadians stand united in sending our love and support to our friends in London."
Russia
Russian President Vladimir Putin condemned the London "terrorist attack" and sent "profound condolences" to the British people, the Kremlin said Sunday.
In a telegram, he told British Prime Minister Theresa May that joint efforts to fight terrorism should be stepped up.
Kremlin spokesman Dmitry Peskov told Russian news agencies: "Putin expresses his profound condolences for the British people and condemns the terrorist attack carried out hours ago in London."
