Mohammed cartoon published in Sweden

Sweden's paper of reference Dagens Nyheter published the controversial drawing, insisting artist Lars Vilks "is not alone in this conflict" after seven Muslims were arrested in Ireland for allegedly plotting his murder.

"A threat against him is, in the end, a threat against all Swedish people," the paper said in an editorial.

Irish police on Tuesday arrested the seven - four men and three women - suspected of conspiracy to murder Vilks because of his cartoon, in an operation coordinated with US and European security agencies.

Police said there was a plot to assassinate Vilks, who has a $US100,000 ($A109,000) bounty on his head from an al-Qaeda-linked group.

US prosecutors also said a Pennsylvania resident Colleen LaRose, who was arrested in October 2009 operating under the online name "JihadJane", had agreed to carry out the murder of a Swedish resident, pledging "only death will stop me."

The Justice Department declined to comment on whether LaRose was connected to the alleged plot to kill Vilks.

Dagens Nyheter called on the Swedish state to give Vilks "all the protection he needs."

It said authorities must take action "against an attack aiming at one of our most fundamental rights, freedom of expression."

The Expressen tabloid also published the cartoon, insisting it was important "to defend freedom of expression which is more and more threatened."

"An open society must show that it will not give in to threats, that it is ready to fight for freedom of expression," added the daily in an editorial.

The regional daily Nerikes Allehanda started the controversy when it first published Vilks' satirical cartoon on August 18, 2007 to illustrate an editorial on the importance of freedom of expression.

That paper did not choose to republish the drawing Wednesday.

I don't think it is relevant to publish the picture," Nerikes Allehanda's chief editor Ulf Johansson, who has also faced threats over the initial publication, wrote in the paper.

"If I were to publish it, it would have another symbolical value than when other papers publish it. Dagens Nyheter has published the picture three to four times already and no one has cared," he added.

The Aftonbladet tabloid, which published the drawing in 2007, also refrained from republishing it Wednesday, with chief editor Jan Hellin insisting "the picture has no news value today."

"Publishing the same picture now would ... only increase the level of conflict and provocation in a situation that requires enlightenment, discussion," he wrote.

Vilks said on Tuesday he was not worried by the arrests in Ireland or the threats on his life. "I'm not shaking with fear, exactly," he told Swedish news agency TT.

He also told the TV4 commercial broadcaster he would consider doing it all over again "if the occasion was right."

"One is allowed to insult all religions but not Islam. That is the exception. There is a problem there," he said.

The threat against Vilks has its parallel in Denmark, where several plots to murder cartoonist Kurt Westergaard have been foiled since his drawing of Prophet Mohammed with a turban in the shape of a bomb was first published in September 2005, along with 11 other drawings focused on Islam.

The threat against Vilks "is very sad, I think," Westergaard told Expressen on Wednesday.

"But I am impressed by his courage and that he refuses to give in," he added.