Francois Fillon has suspended his presidential campaign in the wake of the Paris shooting which killed one policeman and injured another, with just two days to go until the bitterly-fought first round vote.
The French contender’s decision came amid a wave of sympathy from leaders around the world, with US president Donald Trump expressing dismay that terrorists had struck again, and sending his condolences to the French people.
Mr Fillon, a conservative who has campaigned against "Islamic totalitarianism," said on France 2 television that he was cancelling his planned campaign stops on Friday.
His far-Right rival Marine Le Pen, who campaigns against immigration and Islamic fundamentalism, took to Twitter to offer her sympathy for law enforcement officers "once again targeted." Speaking after a television appearance, she said she was "deeply angry" as well as sad for the police victims "because not everything is done to protect our compatriots. They need more than our compassion."
She cancelled a minor campaign stop, but scheduled another.
Centrist candidate Emmanuel Macron offered his thoughts to the family of the dead officer, while Socialist Benoit Hamon tweeted his "full support" to police against terrorism.
The two top finishers in Sunday's election will advance to a runoff on May 7.
President François Hollande scheduled an emergency meeting, saying police were convinced that the attack was “terrorist in nature”.
“A national tribute will be paid to this policeman who was killed in such a cowardly way,” he said. In Washington, Mr Trump was about to enter a press conference with Paolo Gentiloni, the Italian prime minister, when the news broke.
“It’s a very, very terrible thing that’s going on in the world today,” said Mr Trump. “But it looks like another terrorist attack. And what can you say - it just never ends.
“We have to be strong and we have to be vigilant. And I’ve been saying it for a long time.”
A Downing Street spokesman said: "The UK strongly condemns the appalling terrorist attack in Paris. The Prime Minister has tonight passed on her condolences to President Hollande."
The Foreign Office urges British tourists to remain vigilant and follow the advice of the local security authorities.
"If you're in the area and it is safe to do so, contact your friends and family to tell them you are safe," the FCO said in a statement.
Australia's prime minister has offered his country's prayers for the police officers who were shot in Paris and urged Australians in Europe to be wary.
Speaking to Australia's Seven Network, Malcolm Turnbull urged Australian travellers to check for security warnings on the Australian Department of Foreign Affairs and Trade website.
He said: "Everywhere - but especially in Europe at the moment - pay close attention to your surroundings."
Mr Turnbull said that regional security will be among the topics he will discuss with US vice president Mike Pence, who will arrive in Sydney on Friday.
Mr Pence also commented on the shooting, saying it is "latest reminder that terrorism can strike anywhere, anytime." He said that the US "will not relent in our effort to end terrorism."
During a speech to business leaders in Jakarta, Indonesia, Mr Pence said that the people of Paris have "our condolences and our prayers." He said the US will continue to cooperate with the Indonesian government to fight against terrorism.