France has declared a state of emergency and closed its borders after dozens of people were killed in violence in Paris.
Around 100 people have reportedly been taken hostage at a theatre after the French capital was hit by a series of attacks.
French president Francois Hollande said he was closing the country's borders and declaring a state of emergency.
Officials have said between 35 to 40 people have been killed, the Associated Press reported.
Officials said shots were fired in at least two restaurants and at least two explosions were heard near the Stade de France stadium, where the national side was playing Germany in a friendly football match.
President Hollande left the stadium, where he had been watching the game, to hold an emergency meeting.
Prime Minister David Cameron said: "I am shocked by events in Paris tonight. Our thoughts and prayers are with the French people. We will do whatever we can to help."
A Foreign Office spokeswoman said: "We are very concerned about the attacks in Paris. We are in close touch with the French authorities and are urgently investigating whether there are any British nationals caught up in this."