Kurdistan is the home province of Mahsa Amini, 22, whose death in morality police custody sparked the nationwide wave of demonstrations. More than 200 people have been killed in Iran’s brutal response to the protests.

Protests have been especially intense in Sanandaj, where rights groups fear heavy casualties and accuse authorities of resorting to shelling neighborhoods.

The Norway-based Hengaw rights group said an Iranian warplane had arrived at the airport in Sanandaj, and buses carrying special forces were on their way to the city.

Amnesty International said it was “alarmed by the crackdown on protests in Sanandaj amid reports of security forces using firearms and firing tear gas indiscriminately, including into people’s homes.”

The Center for Human Rights in Iran said there was a risk of a similar situation in Sistan-Baluchistan province in the southeast, where activists say more than 90 people have been killed since Sept. 30.

“The ruthless killings of civilians by security forces in Kurdistan province, on the heels of the massacre in Sistan-Baluchistan province, are likely preludes to severe state violence to come,” said its director Hadi Ghaemi.

Among those arrested in the security crackdown was the daughter of Iran’s former president Akbar Hashemi Rafsanjani. Faezeh Hashemi, 59, a former member of parliament and a women’s rights activist, was detained in Tehran on Sept. 27 for inciting residents to take part in demonstrations. Judicial authorities said she had been charged with “collusion, disruption of public order, and propaganda against the Islamic republic.”