Israel's existence is an "insult to all humanity," Iran's president said Friday in one of his sharpest attacks yet against the Jewish state, as Israel openly debates whether to attack Iran over its nuclear program.

Mahmoud Ahmadinejad said confronting Israel is an effort to "protect the dignity of all human beings."

"The existence of the Zionist regime is an insult to all humanity," Ahmadinejad said. He was addressing worshippers at Tehran University after nationwide pro-Palestinian rallies, an annual event marking Quds (Jerusalem) Day on the last Friday of the holy month of Ramadan.

Israel considers Iran an existential threat because of its nuclear and missile programs, support for radical anti-Israel groups on its borders and repeated references by Iranian leaders to Israel's destruction. Ahmadinejad himself has repeatedly made such calls, as has Iran's Supreme Leader Ayatollah Ali Khamenei.

Iran has denied allegations that it is seeking to build nuclear weapons, saying its nuclear program is peaceful and aimed at producing electricity and radioisotopes used to treat cancer patients.

Israel has been carrying on an increasingly public debate about whether to attack Iran's nuclear facilities. Israel's official position is to favour diplomatic and economic measures to persuade Iran to halt its uranium enrichment program, but Israel insists that Iran must not be allowed to obtain nuclear weapons. Israeli leaders say "all options are on the table," a clear reference to a military strike, if they determine that other measures have failed.

Iran has warned it would hit back at Israel if it is attacked, also threatening to strike at American interests in the region.

Ahmadinejad called Israel "a corrupt, anti-human organized minority group standing up to all divine values."

"Today, confronting the existence of the fabricated Zionist regime is in fact protecting the rights and dignity of all human beings," said Ahmadinejad, with a black and white scarf many Palestinians wear around his neck.

Demonstrators in Tehran set U.S. and Israeli flags on fire and chanted "Death to the U.S." and "Death to Israel" during their pro-Palestinian rally.

Iran and Israel have been bitter enemies for decades. Khamenei has called Israel a "cancerous tumour" that must be wiped out.

Tensions between Iran and Israel have intensified since 2005, when Ahmadinejad said in a speech that Israel will one day be "wiped off the map." The Iranian president has also described the Holocaust, when 6 million Jews were killed by German Nazis and their collaborators during World War II, as a "myth."