 In December 2006, Ahmadinejad advised officials not to disturb students who engaged in a protest during a speech of his at the Amirkabir University of Technology in Tehran, although speakers at other protests have included among their complaints that there had been a crackdown on dissent at universities since Ahmadinejad was elected.In April 2007, the Tehran police, which is under Khamenei's supervision, began a crackdown on women with "improper hijab.