Lion-emblazoned flags of pre-revolution Iran fluttered in cities across the world on Saturday as demonstrators took to the streets a week after the start of the latest war in the Middle East.

Europe, Africa, and the Americas saw demonstrations, with some protesting against Iran's Islamic regime, others railing against the war, and some in support of Iran's late supreme leader Ali Khamenei, who was killed in the first US-Israeli strikes of the conflict.

In the US, protesters carried Iranian, Lebanese, and Palestinian flags and signs saying, "Iran is not our enemy" and "No war on Iran" in downtown Detroit, Michigan.

In Washington DC, demonstrators gathered at the National Mall carrying US, Israeli, and Iranian flags, with some protesters painting the colors of the Iranian flags on their cheeks.

In Boston, Iranian Americans gathered at Copley Square to call for the fall of the Islamic republic.

Outside the US consulate in Mexico City, protesters carried a placard with pictures of US President Donald Trump and Israeli Prime Minister Benjamin Netanyahu with blood-soaked palms over the word "assassins."

There, the protesters also kicked piñatas with images of the two leaders.

Paris saw two demonstrations: one supporting the US-based Reza Pahlavi – the son of the late shah – to head up a transition, and another denouncing that scenario.

"I support Pahlavi, who is calling for a revolution," Masoud Ghanaatian (35), a student, told AFP at a protest in southern Paris, where participants carried photos of the late shah's son and waved US, Israeli, and pre-revolution Iran flags.

"He's a democrat. He can oversee a transition and promises to organise elections."

But farther north, protesters wearing yellow vests reading "Free Iran" showed off stickers on their hands that read, "No Shah, no Mullah."

In Amsterdam, protesters snaked along one of the city's canals, calling on the government to invite Pahlavi to the country and close the Iranian embassy.

In South Africa – which has dragged Israel to the International Court of Justice, accusing it of genocide during the Gaza war, a charge Israel denies – dozens gathered in front of the US consulate in Johannesburg, holding up photos of Khamenei, the Islamic republic's flag, and signs bashing Israel.

In Cape Town, Iranian pro-democracy activists and supporters of Israel waved Israeli flags and chanted slogans in the Albert Waterfront shopping mall, with counter-protesters carrying signs denouncing Israel in support of the Palestinians.

Meanwhile, in Israel, anti-war activists and police scuffled during a protest against the war in HaBima Square in Tel Aviv.