Iranians on Friday marked the anniversary of the country's 1979 Islamic Revolution with nationwide celebrations and mass rallies that saw people step on large U.S. flags laid out on the streets while President Hassan Rouhani called the new American administration "a problem."

This year, the anniversary came against the backdrop of remarks by President Donald Trump, who has already engaged in a war of words with Iran's leadership and put Tehran "on notice" over its recent ballistic missile test.

At the Tehran rallies Friday, demonstrators chanted traditional slogans against the United States and Israel, and later, hundreds of thousands marched toward the city's central Azadi Square, where Rouhani addressed the crowds, telling them that Iran will strongly answer any threat from its enemies.

"All of them should know that they must talk to the Iranian nation with respect and dignity," Rouhani declared. "Our nation will strongly answer to any threat. (Iranians) will resist before enemies until the end."

Rouhani called Iran the home of "lions" but said the country does not seek hostility. "We are not after tensions in the region and the world. We are united in the face of bullying and any threat."

Many of the marchers carried the Iranian flag, others had banners and posters with revolutionary slogans. Printed U.S. flags and pictures of current and former U.S. presidents lay scattered on the streets - so they could be trampled by the marchers.

Iran and the U.S. have not had diplomatic relations since 1979, when Iranian students stormed the American Embassy and took 52 Americans hostage for 444 days.

Friday's rallies commemorated Feb. 11 of that year, when followers of Ayatollah Ruhollah Khomeini ousted the U.S.-backed Shah Reza Pahlavi. The United States helped orchestrate the 1953 coup that overthrew Iran's popular prime minister, Mohammad Mossadegh, which brought Pahlavi to power and set the stage for decades of mistrust between the countries.

Some of the posters distributed in English on Friday read: "Thanks to American people for supporting Muslims."

Another one with a picture of Trump said: "Thanks Mr. Trump ... for revealing the face of the U.S." - a reference to remarks by Ayatollah Ali Khamenei, Iran's supreme leader, earlier this week.

Khamenei said on Tuesday that the "newcomer" Trump has shown the "real face" of the United States. He spoke after Trump tweeted - following a ballistic missile test by Iran - that Iranians were "playing with fire," saying they "don't appreciate how 'kind' President (Barack) Obama was to them. Not me!"

Trump has repeatedly criticized the 2015 nuclear agreement between Iran, the U.S. and five other world powers, in which Tehran agreed to curb its uranium enrichment in exchange for the lifting of international sanctions, but he has not said what he plans to do about it.

His administration said Iran was "on notice" over the missile test, and imposed new sanctions on more than two dozen Iranian companies and individuals.

In Tehran, some of the demonstrators threw balls and darts targeting pictures of Trump and Israeli Prime Minister Benjamin Netanyahu. Others burned an American flag. The semi-official ILNA news agency reported that an Israeli flag was also burned.

Many ranking officials attended the ceremony in Tehran, including Gen. Qassem Soleimani who heads the Iranian Revolutionary Guard's Quds Force, which focuses on foreign operations such as the war in Syria and Iraq's fight against the Islamic State group where the Shiite power Iran supports Iraq's government.

Rouhani told reporters prior to addressing the crowds that Iranians will make the U.S. regret using threatening language, according to the semi-official ISNA news agency.

"Anyone who speaks the language of threat to this nation, the Iranian nation will make him regret" it, he said, without elaborating.

"This presence (of demonstrators) is a response to wrong comments by new leaders in the White House, and they announce with their presence to the world that they (U.S. leaders) should talk with respect and not use threatening language to the Iranian nation," Rouhani added.

Iranian state television aired footage of commemorations in Tehran and other cities and towns across the country, many of them held in sub-zero temperatures.

In the central city of Kashan, the official IRNA news agency said the country's prosecutor general, Mohammad Jafar Montazeri, told reporters that members of the Islamic State group have been arrested near Tehran. "They planned to sabotage" the anniversary rallies, he said.

And Khamenei's senior adviser, Gen. Rahim Safavi, said during a similar rally in the southern city of Ahvaz that the "evil triangle" or America, Britain and Israel "cannot create a serious military threat against Iran."

Tehran resident Mohammad Soufi, 33, a medical lab technician, said Trump's recent stance encouraged him and his wife to participate in the rally this year.

"We did not participate in the rally for more than 10 years," he said. "This year my wife told me: 'Let's go out to show to the world, particularly Trump, that we love our county despite differences'."

Sorraya Khalili , a 44-year-old hairstylist, said she was out to support the government and object to the "U.S. bullying of Iran."

"Why people like Trump think they can make decisions for the entire world? Iran is an independent country like the United States," she added. "I wish Americans get to visit Iran to find out we are similar to them; we warmly welcome our guests and respect them."

Foreign Minister Mohammad Javad Zarif posted a photograph on his Twitter account showing protesters with posters with the words: "American people are welcome and invited to visit Iran."

Zarif also said that Iranians on their anniversary praised American people for rejecting Trump's executive action on the visa ban. Iran was among the seven Muslim-majority countries affected by the ban, which remains suspended while U.S. courts debate its legality.

Text from the AP news story, Iranians trample on US flag, mark 1979 Islamic Revolution, by Amir Vahdat.

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