President Francois Hollande vowed Tuesday that France would "never yield" to terror in an emotional tribute to three police officers shot dead in an Islamist killing spree.

The Marseillaise anthem rang out under grey skies as a grim-faced Hollande pinned the country's highest decoration, the Legion d'honneur, onto coffins draped in the red, white and blue flag, surrounded by weeping families and uniformed colleagues.

Two policemen, Franck Brinsolaro, 49 and Ahmed Merabet, 40, were killed during the attack on Charlie Hebdo.

The third police officer Clarissa Jean-Philippe, 26, originally from the French Caribbean island of Martinique, was gunned down the next day when she arrived on the scene of a car accident. Many believe her killer was on his way to a Jewish school down the road.

"That woman saved our children," one parent told AFP.

At the Paris police headquarters pallbearers marched slowly through the square to the strains of a funeral march past a huge Tricolore flag fluttering lightly in the breeze.

"They died so that we could live in freedom," Hollande said of the police officers.