Hundreds of thousands of people took part in rallies across Iran on Sunday to mark the 45th anniversary of the 1979 Islamic Revolution.

The commemoration of the toppling of the US-backed monarch and the takeover by the Islamic cleric Ayatollah Khomeini comes amid rising tensions across the Middle East over Israel's continued war with Hamas in the Gaza Strip.

How was the anniversary marked?

Sunday's processions took place across the country, with major streets and squares decorated with flags, balloons and banners with revolutionary and religious slogans.

In Tehran, crowds waved Iranian flags, chanted slogans, and carried placards with the traditional phrases "Death to America" and "Death to Israel" written on them.

Some burned US and Israeli flags, a common practice during pro-government rallies.

The Iranian military displayed a range of domestically produced missiles, including the Qassem Soleimani and Sejjil ballistic missiles, the Simorgh satellite carrier and drones.

During the celebrations, a paratrooper jumped from a plane while displaying a Palestinian flag.

The marchers included soldiers, students, clerics and senior political and military officials, amid a heavy security presence.

Black-clad women with small children were among those attending, many carrying portraits of Supreme Leader Ayatollah Ali Khamenei.

State TV claimed that "millions participated in the rallies" across the country, showing footage of large crowds in several cities.

Officials, marchers highlight Israel-Gaza conflict 

President Ebrahim Raisi, along with other high-ranking officials, attended the Tehran rally.

Raisi used a speech to accuse the United States and some other Western countries of backing "the Zionist regime's (Israel) crimes against humanity in Gaza."

State media published a picture of some marchers hanging an effigy of Israeli Prime Minister Benjamin Netanyahu by a noose.

Israel's four-month-old war on the Palestinian militant group Hamas in Gaza has sparked a wider regional conflict, with groups backed by Iran mounting attacks on Israeli and US targets.

Backing the Palestinian cause has been a pillar of the Islamic Republic since the revolution, and a way for the Shi'ite-dominated country to position itself as a leader of the Muslim world.

Hamas is part of Iran's "Axis of Resistance", a regional alliance that includes Lebanon's Hezbollah, the Syrian government of President Bashar al-Assad, Shi'ite militia groups in Iraq and the Houthis who control a large part of Yemen.

What was the Islamic Revolution?

The Islamic Revolution began with widespread unrest in Iran over the rule of Shah Mohammad Reza Pahlavi.

The monarch, terminally and secretly ill with cancer, fled the country in January 1979.

After days of mass demonstrations and confrontations between protesters and security forces, Ayatollah Khomeini, who had been expelled in 1954 under a series of reforms, returned from exile. The government fell on February 11, 1979.

In recent years, Iran's relations with the West have deteriorated over Tehran's controversial nuclear program, human rights violations, and its support for militant groups in the Middle East.

mm/lo (AP, dpa, Reuters)