Two brothers wanted for a bloody attack on the offices of French satirical newspaper Charlie Hebdo were killed on Friday when anti-terrorist police stormed their hideout, while a second siege ended with the deaths of four hostages.

The violent end to the simultaneous stand-offs northeast of Paris and at a Jewish supermarket in the capital followed a police operation of unprecedented scale as France tackled one of the worst threats to its internal security in decades.

With one of the gunmen saying shortly before his death that he was funded by al-Qaida, President Francois Hollande warned that the danger to France — home to the European Union's biggest communities of both Muslims and Jews — was not over yet.