JERUSALEM—Israel's prime minister lambasted German poet and Nobel Prize laureate Günter Grass on Thursday for saying Israel is a threat to world peace and for calling for international oversight of both Israeli and Iranian nuclear facilities.

The 84-year-old Mr. Grass published a poem in a German newspaper on Wednesday in which he questioned how Israel could call for ending Iran's nuclear program while holding what is widely believed to be its own atomic arsenal.

Mr. Grass said he wrote the poem, titled "What Must Be Said," after Berlin sold Israel submarines that could launch nuclear warheads and that could potentially be used in an attack on Iran. He noted that for years he resisted criticizing Israel's nuclear program for fear of being labeled an anti-Semite.

In the poem, published in the Sueddeutsche Zeitung and Italy's La Repubblica, among others, Mr. Grass said "the nuclear power Israel is endangering the already fragile world peace."

He also called for "unhindered and permanent control of Israel's nuclear capability and Iran's atomic facilities through an international body."

Benjamin Netanyahu blasted Mr. Grass for comparing Israel to Iran.

"Günter Grass's shameful moral equivalence between Israel and Iran, a regime that denies the Holocaust and threatens to annihilate Israel, says little about Israel and much about Mr. Grass," Mr. Netanyahu said.

He also noted that Mr. Grass, late in his career, admitted to serving in the Nazi paramilitary unit the Waffen SS.

"So for him to cast the one and only Jewish state as the greatest threat to world peace and to oppose giving Israel the means to defend itself is perhaps not surprising," the Israeli leader added.

Israel has never admitted it has nuclear weapons, preferring a policy of nuclear ambiguity. In 1986, technician Mordechai Vanunu carried hundreds of pictures he took of the Israeli nuclear reactor out of the country and gave them to the London Sunday Times. From his photos and information, experts concluded Israel had hundreds of nuclear bombs.

Israel has also ignored calls to join the nonproliferation treaty, which requires members to open nuclear facilities to inspection and to disarm.

Tehran claims its nuclear program is for peaceful purposes, but Israel and the West believe it is pursuing atomic weapons. Israel has threatened military action if international sanctions and diplomacy fail to curb Iran's nuclear ambitions.

Mr. Grass established himself as a leading literary figure with "The Tin Drum," published in 1959, and won the Nobel Literature Prize in 1999. He urged fellow Germans to confront their painful Nazi history in the decades after World War II. He admitted to his SS service in a 2006 autobiography.

Mr. Netanyahu's comments joined a chorus of condemnations from the Jewish community and German leaders.

Abraham Foxman, national director of the Anti-Defamation League, called Mr. Grass's comments "shocking."

"Grass appears convinced that Israel is the wrongdoer at a time when most responsible countries and people are calling on Iran to abandon its nuclear-weapons ambitions," Mr. Foxman said.

Efraim Zuroff, who leads the Nazi-hunting Simon Wiesenthal Center in Jerusalem, said Mr. Grass' poem is a sign of Israel "becoming the whipping boy for the frustrations of those who are sick of hearing about the Holocaust."

The head of the German Parliament's foreign-affairs committee—lawmaker Ruprecht Polenz, a member of Chancellor Angela Merkel's Christian Democrats—told the daily Mitteldeutsche Zeitung that Mr. Grass is a great author, "but he always has difficulties when he speak about politics and mostly gets it wrong."

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