Syrian security forces and students with knives attacked a protest against President Bashar al-Assad at Aleppo University early on Thursday, killing at least four people and arresting 200, according to activists and Internet videos.

Security forces raided the campus and fired at hundreds of students marching in support of the 14-month-old revolt against four decades of Assad family rule, the British-based opposition Syrian Observatory for Human Rights said.

The raid followed an attack on the student protesters by pro-Assad students armed with knives, it said.

Videos of an early morning protest showed students marching in the dark, as bursts of gunfire drowned their chants. Student activists also uploaded a picture of one young man killed, his shirt drenched in blood.

The Observatory, which has a network of activists across Syria, said more student protests had erupted later to denounce the overnight assault and security forces were firing tear gas.

Footage and accounts by activists are hard to verify conclusively because the government restricts media access.

Anti-Assad protests have flared at Aleppo University almost every day for several months, often led by youths who hail from rebellious hotspots such as the northern province of Idlib province and Deraa in the south, the cradle of the revolt.

There was no immediate word on Thursday’s violence from the government or official media.

Aleppo, Syria’s business hub, has been relatively calm during the uprising, compared to embattled cities elsewhere, but the university campus had seen frequent non-violent protests.

The revolt began in March 2011 with peaceful demonstrations inspired by a wave of Arab unrest, but has become increasingly militarised in response to Assad’s violent crackdown.

In Aleppo, security forces had used tear gas and batons to disperse student protests, but have adopted tougher tactics in the last few days, prompting students to stage marches in the middle of the night under cover of darkness, activists said.

The Observatory cited student activists saying security forces had shut the university until May 12 and ordered students out of dormitories that had been used to launch protests.