Hundreds of thousands of Iranians, including President Hassan Rouhani, took part in massive rallies across the country on Friday to encourage Palestinians to keep up their struggle despite the Israeli assault on Gaza.

Footage from Iranian state television showed massive crowds demonstrating in the capital Tehran, chanting "Death to Israel" and "Death to America." Images also showed Iranians carrying pictures of Palestinian children killed in Gaza. State-run Fars News Agency said "millions" of people joined the rallies nationwide.

The rallies were part of Al-Quds Day (“Jerusalem Day”), Iran’s annual day of solidarity with the Palestinian cause that was introduced in 1979 by the Islamic Republic’s founder, Ayatollah Khomeini.

The event took on added significance this year given the Israeli government’s ongoing offensive in Gaza, where it has killed 826 people as of Friday, most of them civilians. The Iranian government has condemned the offensive and expressed support for the Islamist group Hamas, which rules Gaza, and which Iran has allegedly armed in the past.

Iran regards Palestine as comprising all of the Jewish state — which it does not recognize — as well as the West Bank and Gaza.

On Friday, protesters carried banners reading "Defending Gaza and Palestine is our religious duty.”

"We are ready to support our Palestinian brothers and sisters in Gaza. We are ready to sacrifice our blood for them," a man in his 40s told state television in the southern city of Zahedan.

People condemned U.S. support for Israel and burned both U.S. and Israeli flags. They also took aim at foreign governments, which they said had remained silent about Israel's "crimes against humanity."

Ayatollah Ahmad Khatami told worshippers at Friday prayers at Tehran University that Muslims around the world should unite against Israel. "Pressure your governments to boycott this regime (Israel). All Muslims should join hands against this regime," he said.

The head of Tehran’s Jewish community, Homayoun Samayeh Najafabadi also spoke at a protest, encouraging Palestinians to keep up their struggle against Israel.

"We, as the representatives of all Iranian Jews, condemn the crimes committed by the Zionist regime in the Gaza Strip and their savage acts and urge the international community to take a stance against such cruel behavior," Najafabadi told reporters.

Iran’s military leaders went further, using the occasion to call for arming Palestinians in the West Bank. That territory is ruled by the other main Palestinian party, Fatah, which has renounced violence against Israel as a means of achieving statehood.

“We believe the West Bank, too, should be armed just like Gaza, and those who are interested in the fate of the Palestinians must work in this respect so that the pains and miseries of the Palestinian people will be lessened,” Brigadier Gen. Amir Ali Hajizadeh, commander of the Revolutionary Guard Air Force, told Fars during the Quds Day rallies.

Israel and the United States have long accused Iran of supplying arms to Hamas, considered by Washington and the European Union as a terrorist group. Tehran denies that charge and says it gives only moral, financial and humanitarian support.

However, Iran's parliament speaker Ali Larijani acknowledged on Thursday that Tehran had in the past provided Hamas with "the technology to manufacture arms."

"There was a time that Hamas needed the know-how ... We gave it to them and today the fighters in Gaza are capable of meeting their needs," Larijani told Iran's Arabic language al-Alam TV.

Wire services. Michael Pizzi contributed to this report.