Thousands of Iranians took to the streets of Iran early Sunday in a show of support for the unprecedented drone and missile attack under way against arch foe Israel.

"Death to Israel!" and "Death to America!" chanted demonstrators in Tehran's Palestine Square shortly after the Revolutionary Guards announced the launch of Operation Honest Promise.

A mural saying "the next slap is fiercer" was unveiled in the square where a huge banner has hung for days calling, in Hebrew, for Israelis to "take shelter".

On Sunday, demonstrators waved Iranian and Palestinian national flags alongside banners reading "God's victory is near".

Iran's attack came in retaliation for an April 1 strike that levelled the five-storey consular annexe of the Iranian embassy in Damascus and killed seven Revolutionary Guards, two of them generals.

Tehran has since vowed to avenge the strike which was widely blamed on Israel.

Iran's supreme leader Ayatollah Ali Khamenei pledged that the "evil (Israeli) regime will be punished".

- 'Self-defence' -

Iranian media described the attack on Israel as "complex" as it also involved Iranian allies in Yemen, Lebanon and Iraq.

"This attack did not come from Iran only, and this regime (Israel) is being punished from four directions," the Tasnim news agency said.

A large crowd of demonstrators gathered outside the British embassy in Tehran.

Supporters of the retaliatory attack also demonstrated in Iran's third largest city Isfahan where Brigadier General Mohammad Reza Zahedi, one of the generals killed in the Damascus strike, is buried.

Demonstrators also gathered near the grave in the southern city of Kerman of prominent Guards commander Qasem Soleimani, who was killed in a 2020 US drone strike in Baghdad.

Tehran had earlier appealed to Washington to keep out of its conflict with Israel but Iranian hopes were dashed after a Pentagon official confirmed that US forces were shooting down Israel-bound drones.

Iran insists it acted in "self-defence" after the targeting of its diplomatic mission in Damascus. It said it hoped its action would prompt no further escalation and "the matter can be deemed concluded."

- War fears -

The latest developments took place against the backdrop of the Gaza war which began with Hamas's October 7 attack on Israel which killed 1,170 people, mostly civilians.

Tehran backs Hamas but has denied any direct involvement in its attack on Israel.

Israel's retaliatory offensive against Hamas has killed at least 33,686 people in Gaza, mostly women and children, according to the Hamas-run territory's health ministry.

Iran does not recognise Israel, and the two countries have fought a shadow war for years.

Anticipation of conflict with Israel had gripped Iran ever since the April 1 strike on its consulate.

"It is better to reach a compromise so that the war does not begin, and innocent people don't die," said Maryam, a 43-year-old private sector worker.

"God willing, our government will favour reason over emotion," said Salehi, a 75-year-old retired government employee in central Tehran.

Ehsan, a 43-year-old university professor, said it was "logical" to retaliate.

"War is always bad and worrying -- a person who has experienced war would never support it, but sometimes to achieve peace, a war is necessary," he added.