Three masked gunmen stormed the offices of the French satirical magazine wielding assault rifles.

They killed 12 and injured 11 more, four of them critically.

It's thought to be France's deadliest terrorist attack in decades.

The French ambassador to Australia, Christophe Lecourtiergreeted visitors sharing their condolences at the embassy Thursday evening.

Mr Lecourtier condemned the attacks and said the gunmen targeted national values that were shared by Australians.

"What has been targeted is French citizens, French journalists, but also some of the most important of our values; freedom of press, freedom of expression," he said.

"This is what the terrorists have tried to kill yesterday in Paris."

Security has been stepped up at French embassies and consulates in the wake of the attack.

"We have, since very early [Thursday] morning, had contact with the AFP in Canberra, in Sydney and also in Melbourne - some security measures have been taken in order to protect those who represent France in this country," he said.

"What has happened in Sydney a few weeks ago, now in Paris, may have belonged to the same sad story."

Mr Lecourtier said hundreds of thousands of French citizens had rallied across the country to show they were united in the face of the attack,

He said the global response had strengthened international unity.

"This is one attack that's succeeded, unfortunately, but many others have been prevented, mostly thanks to the good co-operation we have in France with our security agencies and overseas with allies like Australia," he said.

"Democracy does not mean we are weak. Even in such difficult times we know that we are stronger than others attacking us in such a shameless way."

Mr Lecourtier, who went to school with the daughter of one of the cartoonists killed, said the historical significance of freedom of expression in France dated back to the French revolution.

Personally, he said he had followed Charlie Hebdo articles and cartoons over the years, which were an important part of the country's modern history.

Four of France's most prominent satirical cartoonists were among the Charlie Hebdo staffers and two police officers killed in the attack.

French police say they have identified three men as suspects.

Mr Lecourtier had been in contact with the French government overnight and hoped police would soon track down the offenders so they could be brought to justice.

He said most organisations which represented France's Muslim population had expressed concern and their condolences over the attack.

The Australian embassy in Canberra was among French embassies throughout the world which lowered their flags as a mark of respect and solidarity after the attack.

Staff began to trickle into the Yarralumla building as Australian Federal Police officers arrived at the embassy about 9am on Thursday.

An AFP spokeswoman said the agency had been liaising with embassy staff and was satisfied with the current security arrangements.

Also in the capital, a quick pencil sketch, drawn by Canberra Times cartoonist David Pope as he watched television reports of the incident on Wednesday night, has gone viral on social media.

Charlie Hebdo gained notoriety in February 2006 when it reprinted cartoons of the Prophet Mohammed that caused fury across the Muslim world.

Museum of Australian Democracy manager of visitor experience Michael Evans, who was executive producer on the museum's current Behind the Lines 2014 exhibition, said freedom of speech and political expression through such cartoons was "extremely important".

"We look at 800 cartoons a year and when you see them together like that you realise how much spread of opinion there is on every issue," he said.

"Some of the images, the caricatures of politicians they come up with you sort of shiver at them, but that's why it's important we have that freedom of speech. Once cartoonists feel they don't have that freedom, it's a very slippery slope."

He said while many cartoonists and publishers acknowledged there were "unwritten rules" when it came to political cartoons on sensitive topics, they believed in freedom of expression and the events in Paris would not force them to back down.