'The whole of Europe has been hit': Hollande
French President Francois Hollande said the attacks in Brussels on Tuesday that killed at least 26 people struck at "the whole of Europe".
"Through the attacks in Brussels, the whole of Europe has been hit," Hollande said in a statement, urging the continent to take "vital steps in the face of the seriousness of the threat".
French Prime Minister Manuel Valls said: "We are at war. Over the past few months in Europe we have endured several acts of war."
France, which neighbours Belgium to the south, was hit by two major terror attacks in 2015 and several of the jihadists behind them came from Brussels.
"France will implacably continue the fight against terrorism both on the international level and at home," said Hollande.
Attacks on November 13 in Paris claimed 130 lives, 10 months after attacks on the satirical newspaper Charlie Hebdo and a Jewish supermarket left 17 dead.
French Interior Minister Bernard Cazeneuve earlier announced that Paris was deploying 1,600 additional police to border crossings and air, sea and rail infrastructure after the Brussels attacks.
Germany and the Netherlands also announced stepped up security measures at borders, airports and rail stations.
© 2016 AFP