Obama to France: 'The United States stands with you'

US President Barack Obama rallied to the support of France on Friday after the bloody end to hostage sieges in Paris, vowing to offer all assistance to the country.

"I want the people of France to know that the United States stands with you today, stands with you tomorrow," Obama said at a speaking engagement in Tennessee, describing France as America's "oldest ally".

"The moment that the outrageous attack took place, we directed all of our law enforcement and counterintelligence operations to provide whatever support that our ally needs in confronting this challenge," Obama said.

"We're hopeful the immediate threat is now resolved. The French government continues to face the threat of terrorism and has to remain vigilant. The situation is fluid," he added.

Meanwhile, the US warned Americans to beware of "terrorist actions and violence" all over the world, following the Paris attacks.

"Recent terrorist attacks, whether by those affiliated with terrorist entities, copycats, or individual perpetrators, serve as a reminder that US citizens need to maintain a high level of vigilance and take appropriate steps to increase their security awareness," the State Department said on Friday. 

The advisory is an update to its "Worldwide Caution" from 10 October 2014.