LONDON, U.K. — Iran’s opposition movement showed it may have staying power Wednesday as thousands of opposition protesters took to the streets alongside a regime-backed demonstration marking the 30th anniversary of the takeover of the U.S. Embassy in Tehran.

A multitude of security forces and plainclothes militias cracked down violently on the protesters, shooting tear gas and leading baton charges throughout central Tehran.

Students defied government warnings and the forced closure of some universities to gather at Tehran and Sharif universities, the Iranian capital’s main campuses. Riot police closed down the city center and assaulted groups wherever they gathered.

Grainy videos streaming out of the Iranian capital on YouTube and Facebook showed gas mask-wearing demonstrators jumping over trash fires as they fled from security forces. Injured members of the public were carried to side streets and parking lots to be treated. Other alleys were transformed into temporary detention centers for demonstrators who were detained by riot police who sallied forth to disperse protesters.

“I have been amazed by the steadfastness of the protesters and their bravery,” said James Spencer, a Middle East expert specializing in defence and security issues. “The regime is weak, they’ve been unable to stop the protests using the current level of force and, as with the Shah, don’t dare increase the level of violence too much for fear that the IRGC [Revolutionary Guards] will refuse.”

One demonstrator freshly returned from the streets described how she disguised herself from traffic cameras used to identify protesters by wearing sunglasses and a gas mask. Golnaz, 23, described how she shouted anti-regime slogans with her boyfriend, and both were hit by tear gas and struck with batons before seeking refuge in a nearby house.

“I lost my mother and another friend while a guard attacked my boyfriend, striking him on the shoulder with a baton and smashing the door’s glass on his head,” she recounted, in an email from Tehran. “He managed to escape inside (the house) however.” Once inside the house, they sat with a number of other protesters in terrified silence.

“There were several harsh knocks on the door but no one dared to open it so they left,” Golnaz recounted. “In between there was the sound of shooting but I’m not sure if they shot anyone. Then there was the sound of female shrieking so we looked from the window and saw this girl with no scarf, messed up and hysterical as if she had been beaten. She was walking shocked and constantly screaming.”

Opposition leader Mehdi Karroubi was attacked by pro-regime plainclothes militiamen, according to some reports that also said he was targeted with tear gas. One picture shows him without his cleric’s turban and sporting a red cut on his forehead.

In another video, he emerges from the sunroof of his car to rapturous applause by his supporters. There were no sightings of Mir-Hossein Mousavi who has maintained a lower profile in recent weeks as calls for his arrest and trial increased.

“It will continue to organize, subvert official commemorations, and press against the prevailing conditions,” said Spencer. “As every year passes, the Neo-Revolutionaries lose demographic weight.”

Iran’s Green Movement has also been called the revolt of the third generation of the 1979 Iranian Revolution. Some 70 percent of Iranians are under 30 years old and have memory neither of the Shah nor of Ayatollah Ruhollah Khomeini, the founder of the Islamic Republic who passed away in 1989.

On the streets of Tehran, demonstrators shouted slogans questioning whether U.S. President Barack Obama is “with us or with them,” in a criticism of the recent nuclear deal offered the Islamic Republic. But they also read Obama’s message commemorating the takeover of the U.S. Embassy in which he urged the Iranian government to consider “what kind of future it is for” as a sign of his support.

“The world continues to bear witness to (the Iranian peoples’) call for justice and their courageous pursuit of universal rights,” Obama said.

Despite demonizing the West, mandating the teaching of Arabic at school and closing down universities during the Cultural Revolution of 1980-83, the authorities have failed to stem the tide of Westernization. Unlike the Shah’s era, Western culture is now piped into Iranian households both from illegal satellite dishes and through the internet.

“We shouldn't get carried away,” said Spencer, referring to suggestions that if Iran’s revolutionaries are successful, they will usher in a pro-Western regime. “They’re Iranians and want their own Iranian republic, which will probably continue in a similar line to the mullahs, just on a nationalist rather than Islamist line.”