Iran's Supreme Leader Ayatollah Ali Khamenei speaks during a meeting in Tehran on Wednesday. Iran has been rocked by unrest since Masha Amini, 22, died on Sept. 16 in police custody in Tehran after being detained for allegedly breaching the country's strict rules on headscarves and modest clothing. ( Office of the Iranian Supreme Leader/The Associated Press) 

Iran suffered a "major disruption" in internet service Wednesday as calls for renewed protests again saw demonstrators on the streets weeks after the death of a 22-year-old woman who had been detained by the country's morality police, an advocacy group said.

The demonstrations over the death of Mahsa Amini have become one of the greatest challenges to Iran's theocracy since the country's 2009 Green Movement protests. Demonstrators have included oil workers, high school students and women marching without their mandatory headscarf, or hijab.

Calls for protests beginning at noon Wednesday saw a massive deployment of riot police and plainclothes officers throughout Tehran, witnesses said. They also described disruptions affecting their mobile internet services.

NetBlocks, an advocacy group, said that Iran's internet traffic had dropped to some 25 per cent compared to the peak, even during a working day in which students were in class across the country.

Despite the disruption, witnesses saw at least one demonstration in Tehran by about 30 women who had removed their headscarves while chanting, "Death to the dictator!" Those cries, referring to Iran's Supreme Leader Ayatollah Ali Khamenei, can result in a closed-door trial in the country's Revolutionary Court, with the threat of a death sentence. 

Lawyers demonstrate in Tehran

Passing cars honked in support of the women despite the threats of security forces. Other women simply continued with their day not wearing the hijab in a silent protest, witnesses said. Demonstrations occurred on university campuses in Tehran as well, online videos purported to show.

Lawyers also peacefully demonstrated in front of the Iran Central Bar Association in Tehran, chanting, "Woman, life, freedom" — a slogan of the demonstrations so far. The video corresponded to known features of the association's building. A later video posted by activists purported to show them fleeing after security forces fired tear gas at them. At least three were arrested, the pro-reform newspaper Shargh reported.

Videos also purported to show demonstrations Wednesday in Baharestan, just southeast of the city of Isfahan, as well as in the southern city of Shiraz and northern city of Rasht, on the Caspian Sea. Gathering information about the demonstrations remains difficult amid the internet restrictions and the arrests of at least 40 journalists in the country, according to the Committee to Protect Journalists.