BERLIN: Peace activists on Monday voiced support in Germany for author Gunter Grass who has been barred from entering Israel over a poem accusing the Jewish state of plotting Iran’s annihilation and endangering world peace.

“It is unacceptable,” said Willi van Ooyen, a spokesman for a group that organises the traditional peace marches held each year on Easter weekend in Germany since 1960.

“Threats and preparations for war poison the political climate,” said Ooyen, referring to concerns that Israel might launch a strike against Iran’s nuclear facilities to stop a suspected weapons programme.

The 84-year-old Grass sparked outrage at home and abroad last week with the publication of a poem titled “What must be said” in which he said he feared a nuclear-armed Israel “could wipe out the Iranian people” with a “first strike”.

Israeli Prime Minister Benjamin Netanyahu described the poem as “shameful”.

Grass, a Nobel literature prize winner, has said he found the personal accusations against him “hurtful”, but he had no plans to back down.

The debate ignited by the poem has not ceased in Germany where Foreign Minister Guido Westerwelle on Sunday penned a commentary that appeared to criticise Grass, without making explicit reference to him.

“Germany has a historic responsibility for the citizens of Israel,” he wrote in the Bild Am Sonntag. “To put Iran and Israel on an equal moral footing is not clever but absurd.”

The country's health minister Daniel Bahr also chimed in calling Israel’s decision to ban Grass “completely exaggerated”, in an interview with daily Die Welt to appear in Tuesday’s edition.

“I can hardly imagine that Mr. Grass has any interest in showing up in Israel,” said Bahr, a member of the FDP liberal party, part of the ruling coalition, according to the newspaper. He also criticised Grass for not being open to listening to others’ opinions.

It is not the first time Grass has sparked outrage. The author of the renowned anti-war novel “The Tin Drum” touched off a firestorm of controversy in 2006 when he revealed, six decades after World War II, that he had been a member of the notorious Waffen SS.

Israel, the sole if undeclared nuclear power in the Middle East, has said it is keeping all options open for responding to Iran's nuclear programme, which it and much of the West says is aimed at securing atomic weapons.

Iran has denied that it is seeking to build a nuclear bomb.