According to witnesses, Iranian security forces deployed to colleges in numerous cities on Wednesday, ramping up attempts to crush more than two weeks of protests sparked by the murder of Mahsa Amini, 22, in the custody of morality police.

The widespread turmoil caused by her death has erupted into the most serious threat to Iran’s clerical leaders in years, with protestors clamoring for the overthrow of the 1979-founded Islamic Republic.

Riot police fanned out in the cities of Urmia, Tabriz, Rasht and the capital Tehran, particularly around universities which have been a focal point of protests in recent days, the witnesses said.

“There are lots of security forces around Tehran University. I am even scared to leave the campus. Lots of police vans are waiting outside to arrest students,” said a student in Tehran.

Rights groups say thousands have been arrested and hundreds injured in the crackdown waged by security forces including the Basij, a volunteer militia affiliated with Iran’s Revolutionary Guards. Rights groups put the death toll at over 150.

Authorities have reported numerous deaths among the security forces, accusing foreign adversaries including the United States of meddling to destabilize Iran.

Videos shared on social media on Wednesday showed high school girls in Tehran taking off their headscarves and chanting “death to (Supreme Leader Ayatollah Ali) Khamenei”.

In a footage said to have been filmed at a school in Shiraz on Tuesday, about 50 female pupils surrounded a member of the Basij who had been invited to give a speech, shouting “Basij get lost” and “death to Khamenei”.

People from different layers of the society across Iran have joined protests since Amini, an Iranian Kurd, died after being detained in Tehran on Sept. 13 for “inappropriate attire”.

The death of a 17-year-old girl since the start of the protests has become another focal point of protester anger, with activists on Twitter saying Nika Shakarami was killed in Tehran while demonstrating over Amini’s death.

State media said on Wednesday a judicial case had been opened into Shakarami’s death, citing officials claiming it had nothing to do with the unrest, and that she had fallen off a roof and her body contained no bullet wounds.