Over 50 thousand police and soldiers have been fully mobilised in France after last night's shooting in Paris.
A police officer was killed and three others were injured in the attack on one of the most famous streets in the world.
A gun and knives have been found in the car of the attacker who was shot dead. A second man wanted in connection with the attack has handed himself in to a police station in Antwerp, Belgium.
Islamic State says it was behind the attack.
It's emerged that the gunman had been held by authorities in February for threatening police - but later freed.
The Champs Elysees shooting comes just days before the country's presidential election.
Kim Buckley has this report:
French President Francois Hollande has given his reaction.
"I am deeply sad tonight," French Pres. Francois Hollande says after police officer killed in Paris shooting https://t.co/Okz2bwUl4f pic.twitter.com/ixNgP8rqE7
— CBS News (@CBSNews) April 20, 2017
And President Trump.
Trump on Paris: "It looks like another terrorist attack. What can you say? It just never ends. We have to be strong" https://t.co/fKajkK4S70 pic.twitter.com/AxrQyTjrV9
— ABC News (@ABC) April 21, 2017
This eyewitness, Dr Angela Maggard, was visiting the city with her family from America and was nearby:
A row has now broken out between politicians ahead of the elections: one of the candidates, Marine Le Pen, who's head of the far right party the National Front - wants the government to immediately reinstate border checks in the wake of the attack.
French prime minister Bernard Caze neuve, speaking here through a translator, wasn't impressed with her tactics:
