French President Francois Hollande delivers a speech at a special congress of the joint upper and lower houses of parliament (National Assembly and Senate) at the Palace of Versailles, near Paris, France, November 16, 2015. [Photo/Agencies]

"Even as we grieve with our French friends ... we can't lose sight that there has been progress," Obama said at a Group of 20 summit, ruling out sending in ground troops.

US Secretary of State John Kerry, visiting Paris to pay respects to those killed in the attacks, said: "Tonight we are all Parisians," and pledged the United States would stand "shoulder to shoulder" with France against Islamic State militants. He is due to meet Hollande on Tuesday morning.

Much of France came to a standstill at midday for a minute's silence to remember the dead, many of whom were young people killed as they enjoyed a night out. Metro trains stopped, pedestrians paused and office workers stood at their desks.

In a sign of life slowly returning to normal, schools and museums reopened after a 48-hour shutdown, as did the Eiffel Tower, which lit up the night sky in the red, white and blue colours of the French flag following two days of darkness.