French media back Charlie Hebdo after new threats
The magazine republished cartoons of the Prophet Mohammed earlier this month at the start of a trial of suspects in the 2015 attack on their Paris office.
While the edition sold out in France, it provoked condemnation from several Muslim countries and Al-Qaeda militants reportedly threatened a repeat of the 2015 massacre of its staff.
The open letter on the front page of the new edition denounces "new totalitarian ideologies, sometimes claiming to be inspired by religious texts".
Urging people to support the magazine, it says: "The enemies of freedom must understand that we are all, together, their steadfast opponents, regardless of our differences of opinion or beliefs."
Twelve people including some of France's most celebrated cartoonists were killed on January 7, 2015, when brothers Said and Cherif Kouachi went on a gun rampage at the magazine's office.
Fourteen people are on trial suspected of helping the Kouachi brothers in that attack and another at a Jewish supermarket two days later.
Charlie Hebdo's head of human resources told Le Point magazine that police had rushed her from her home after she received death threats they judged to be credible.
She told Le Point there was "crazy amount of hatred" towards the magazine.
"Charlie Hebdo is once again threatened by terrorist organisations," editorial director Laurent Sourisseau, who was badly wounded in 2015, told AFP.
"Threats that constitute a real provocation in the midst of the trial of the January 2015 attacks."
The letter supporting Charlie Hebdo is signed by major newspapers, magazines and broadcasters, who will republish it.
"It seemed necessary to us to suggest to the media to think about the collective response," Sourisseau said.