Authorities in Hamburg have two "young men" in custody after rocks and an "incendiary device" were thrown through a window of the regional daily newspaper Hamburger Morgenpost.

The paper, known in the region as MOPO, had published cartoons on Thursday that appeared in Charlie Hebdo, showing solidarity with the slain cartoonists.

AFP:

"Rocks and then a burning object were thrown through the window," a police spokesman told AFP.

"Two rooms on lower floors were damaged but the fire was put out quickly."

The Hamburger Morgenpost, known locally as the MOPO, had splashed the Charlie Hebdo cartoons on its front page after the massacre at the Paris publication, running the headline "This much freedom must be possible!"

Police said the attack had occurred at about 0120 GMT and that two young men seen acting suspiciously near the scene were detained. State security has opened an investigation, a spokesman added.

Whether there was a connection between the Charlie Hebdo cartoons and the attack was the "key question", the spokesman said, adding that it was "too soon" to know for certain.

Police declined to provide further information about the suspects.

No one at the Hamburger Morgenpost, which has a circulation of around 91,000, could immediately be reached for comment.

"Thick smoke is still hanging in the air, the police are looking for clues," the newspaper said in its online edition, under the headline "Arson attack on the MOPO - Due to the 'Charlie Hebdo' cartoons?".

It published a picture showing firefighters in the courtyard of the building with a caption saying the incendiary device had been hurled into the basement.

Given the relative crudity of the firebomb and the small amount of damage, it is probable that the culprits were amatuers and not trained terrorists. But that makes the attack more significant.

Europe is gripped by a fever, and if jihadist-wannabees like these kids can be inspired to firebomb a newspaper, there is a potential for hundreds of these kinds of attacks all over the continent. .European Muslims - perpetually outraged, perpetually aggreived about something - don't need much of an excuse to strike at Western Civilization. And there is no more obvious and symbolic target than a newspaper.

Hamburger Morgenpost was brave to publish the cartoons. And they believed they had taken adequate security precautions. But there will be no true security until authorities confront  the evil in their midst and destroy it.