At least 18 people were killed in a series of gun attacks across Paris on Friday, as well as explosions outside the national stadium where France was hosting Germany.
Police said at least 15 people had been killed at the Bataclan concert hall in central Paris, only around 200 metres from the former offices of Charlie Hebdo which were attacked by jihadists in January.
Police said a hostage scenario was ongoing at the venue, which is in an area known for its busy nightlife.
Three people were killed in an explosion outside the Stade de France north of the capital, police said, during a match between Germany and France.
Spectators flooded the pitch as news of the attacks spread. Organisers started evacuating the stadium by three doors.
Another attack was reported at the Petit Cambodge restaurant, not far from the Bataclan venue.
An AFP reporter outside the Bataclan said there were armed police and some 20 police wagons with their lights flashing around the scene.
Stunned onlookers had begun to emerge from nearby bars, while many others continued to eat their meals in restaurants, apparently unaware of the carnage that had taken place only a few metres away.
President Francois Hollande and Interior Minister Bernard Cazeneuve announced that a crisis cell had been set up.
"The president of the Republic, the prime minister, the interior minister are in a inter-ministerial crisis cell," the government said in a statement.
France has been on high alert since the jihadist attacks in January against Charlie Hebdo magazine and a Jewish supermarket that left 17 dead.
Several other attacks have been foiled through the year.
More than 500 French fighters are thought to be with IS in Syria and Iraq, according to official figures, while 250 have returned and some 750 expressed a desire to go there.
The government announced last week that it was restoring border checks as a security measure for UN climate talks that start in Paris at the end of this month.