CAIRO, Oct 20 (Reuters) - Egyptian security forces fired bird shot and tear gas to prevent supporters of deposed Islamist President Mohamed Mursi from marching on Sunday to the site of a protest camp that was destroyed two months ago, a Reuters witness said.
The crowd of about 500 people were students from Al-Azhar University, the historic seat of Sunni Muslim learning.
A Reuters witness said he could smell teargas and could see students throwing rocks at riot police stationed outside the gates of the university, which is in the same Cairo suburb as the Rabaa al-Adaweya mosque, the scene of a former pro-Mursi protest camp.
"Rabaa Square is completely off-limits," a security source said. "Protesters are not allowed to move inside it." He said four students had been arrested.
Riot police were throwing stones back at the students.
The students had been protesting on campus in support of Mursi of the Muslim Brotherhood, who was overthrown by army chief General Abdel Fattah al-Sisi on July 3. Graffiti scrawled on university buildings refers to Sisi as a murderer and traitor.
The army rejects the claim that it had deposed Mursi in a coup and says it was responding to the will of the people after mass protests against his rule.
Army-backed authorities have cracked down hard on the Brotherhood, crushing two pro-Mursi protest camps on Aug. 14, killing hundreds and arresting thousands. (Reporting by Michael Georgy and Yasmine Saleh; Writing by Maggie Fick; Editing by Yara Bayoumy and Janet Lawrence)