DUBAI: Weeks of protest in Iran entered a more violent phase on Sunday as students defied an ultimatum by the Revolutionary Guards and were met with tear gas, beatings and gunfire from riot police and militia, social media videos showed.

The confrontations at dozens of universities prompted a threat of a tougher crackdown in the seventh week of demonstrations since 22-year-old Mahsa Amini died after she was arrested by the morality police for attire deemed inappropriate. Iranians from all walks of life have been protesting since Amini’s death. What began as outrage over Amini’s death on Sept. 16 has evolved into one of the toughest challenges to clerical rulers since the 1979 revolution, with some protesters calling for the death of Supreme Leader Ayatollah Ali Khamenei.