Egyptian police fired tear gas at protesting students at Cairo's al-Azhar university on Wednesday hours after authorities announced the detention of Muslim Brotherhood leader Essam El-Erian, part of a crackdown against the Islamist movement.
Students at the country's top institution for Islamic teachings have been demonstrating for weeks in support of ousted Islamist president Mohamed Morsi, whom the army toppled in July after mass protests against his rule.
The head of al-Azhar university had called on the police to enter campus grounds to "protect souls and properties," according to an interior ministry statement.
Demonstrations at Al-Azhar are a sensitive matter because the institution has historically toed the government line.
Erian, the deputy leader of the Brotherhood's Freedom and Justice party, was taken into custody early on Wednesday from a residence in New Cairo where he had been in hiding.
"He's been arrested and details will soon be released," an Interior Ministry source told Reuters.
Local media circulated a photo of what they described as the moment he was arrested, showing a smiling Erian standing next to a bed with two packed duffle bags.
Many Brotherhood leaders have been detained since the army deposed Morsi, Egypt's first freely elected president, and declared a road map leading to elections.
Critics of the government say it is becoming more authoritarian, stifling dissent and limiting freedom of speech.
Human rights groups and some liberal politicians have expressed alarm over a draft law under debate that would place restrictions on protests.
New York-based Human Rights Watch said the law would give police carte blanche to ban protests in Egypt.
"This draft law would effectively mandate the police to ban all protests outright and to use force to disperse ongoing protests," said Sarah Leah Whitson, Middle East director at Human Rights Watch.
"The final law will be an important indicator of the extent to which the new government is going to allow for political space in Egypt."
The trial of three senior Muslim Brotherhood leaders on charges of inciting violence was halted on Tuesday after the judge withdrew.