France will take "all measures" to ensure the safety of Sunday's march to be attended by European leaders after this week's attacks and is maintaining its highest possible security level in the Paris area, the interior minister said.

Speaking on Saturday after an emergency meeting with French President Francois Hollande, Bernard Cazeneuve said "we want to keep the high level of mobilization and vigilance."

French forces were Saturday frantically hunting for the girlfriend of an Islamist gunman as the country mourned 17 dead in three blood-soaked days that shook the nation to its core.

After President Francois Hollande warned the threats facing France "weren't over" and Islamist groups issued chilling warnings of fresh attacks, authorities pursued Hayat Boumeddiene, said to be "armed and dangerous."

The United States on Friday warned Americans to beware of "terrorist actions and violence" all over the world, following the attacks on the Charlie Hebdo magazine and a Jewish supermarket in Paris.

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

Australia grieves with France over the attack on satirical magazine Charlie Hebdo, Prime Minister Tony Abbott said Saturday, adding he had discussed the evolving international terror threat with President Francois Hollande.

Abbott and Hollande spoke on the telephone on Friday, the Prime Minister's office said in a statement, saying the French leader had updated him on the situation as it was unfolding and other recent attacks.

French imams condemned violence committed in the name of Islam during Friday prayers as the country reeled from the double hostage dramas that followed the massacre at Charlie Hebdo magazine.

The same message -- distancing the country's five million Muslims from the jihadists responsible for the attacks -- was relayed at more than 2,300 mosques across France.

Israeli Prime Minister Benjamin Netanyahu asked France Friday to maintain tight security on Jewish sites after a series of incidents that included hostages being killed at a kosher store in Paris.

"Prime Minister Netanyahu asked the president of France to keep up the increased security on Jewish institutions even after things return to normal," Israeli government sources told AFP following a telephone conversation between Netanyahu and Francois Hollande.

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 combat the threat of militant Islamists.

"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."

A gunman robbed a jewelery store in the southern French city of Montpelier on Friday and took two women hostage, a judicial source said -- but stressed the incident "had no link" to the twin hostage dramas around Paris.

"It was a robbery, it has nothing to do with what is happening in Paris," prosecutor Christophe Barret told AFP.

One of the suspects in the attack against French satirical magazine Charlie Hebdo studied in Yemen where he attended al-Qaida training camps, Yemeni security sources and a classmate said Friday.

Said Kouachi appeared at various times between 2009 and 2013 in the troubled Arabian peninsula country, firstly as a student at a Sanaa university known as a hotbed of Islamic fundamentalism and then at al-Qaida training camps in the south and southeast, the sources said.

Elite French police stormed a printworks and a Jewish supermarket Friday, killing two brothers wanted for the Charlie Hebdo attack and a gunman linked to them in a dramatic end to twin sieges that rocked France.

As shots and explosions rang out in the City of Light, five people, including the gunman, were found dead in the aftermath of the assault on the Jewish store in eastern Paris and several captives were freed, security sources said.