Syrian security forces and students armed with knives have attacked a protest march at Aleppo University, killing at least four people who were protesting against President Bashar al-Assad's rule, activists have said.
Several others were wounded during the pre-dawn raid early on Thursday, with activists saying that as many as 200 demonstrators were arrested.
Thaer al-Ahmed, a local activist, said that security forces and armed government supporters fired tear gas and live ammunition to disperse the students at Aleppo University after entering the students' residences late on Wednesday night.
Al Jazeera's Rula Amin, reporting from Beirut, said security forces swept through dormitories at the university after anti-government protests were held on campus.
"The government launched a huge arrest campaign on the university and four students were killed when students began to protest what was happening," Amin said.
According to Amin, the violence in Aleppo was "very significant" because the city had so far not been marked by the mass anti-government protests that have erupted across the country over the past year.
"Aleppo is a city that has so far not joined the revolution," our correspondent added.
Video posted on the Internet showed students chanting against four decades of Assad family rule but being drowned out by gunfire.
Activists also posted images of a dead student, his shirt drenched in blood, and what they said was a burning dormitory.
Raids and intermittent gunfire continued for about five hours through early Thursday, students said.
The Syrian Observatory for Human Rights (SOHR), a UK-based opposition group, reported that 28 students had been wounded in the clashes, three of them critically.
The Local Co-ordination Committees (LCC), activist umbrella group, also confirmed the raid.
"Regime forces demanded through loudspeakers that the dorms be evacuated, then began detaining the students," the LCC said in a statement.
The Syrian government offered no comment on the clashes.
The deadly incident has prompted the University of Aleppo to announce on its website that it was suspending classes until after final exams on May 13.
Small protests were held in several other universities on Thursday, including in Deir Ezzor, Damascus and Deraa, activists said.
The exiled opposition Syrian National Council called for a nationwide campus strike in solidarity with the Aleppo students.
Major General Robert Mood, the head of the UN monitoring mission in the country, meanwhile, said that the observers' mission in the country was having "a calming effect".
Violence was reported on Thursday, however, from the flashpoint town of Homs. The Reuters news agency reported that continuous gunfire could be heard in the Khalidiyeh neighbourhood, and that there was the occasional sound of a shell exploding.
In-depth coverage of escalating violence across Syria
Monitors have been permanently present in Homs for several days.
Explosions also hit the Jabal al-Zawiya area of Idlib, and security forces killed at least one woman there on Thursday, the SOHR said. Several people were also arrested in the town.
Clashes were also reported from the central city of Palmyra.
The SOHR said that ten people, including an army defector and a soldier, were killed in violence on Thursday.
Mood, speaking in Homs on Thursday, said that observer mission was growing at a steady pace, with a total of 50 monitors in the country which would be doubled within weeks.
"We have reinforced our permanent teams in Hama and Deraa with an extra two monitors in each city," he said from the al-Safir hotel in Homs, where six monitors are based permanently.
Around 300 monitors will be deployed by the end of May.
Earlier on Thursday, during a visit to Hama, Mood said Syrian government forces had been working in line with a tentative peace plan.
"There have been steps taken by the government forces on the ground that indicate a better willingness to live up to the commitments made in the agreement," he said, giving no details.
Residents of Hama said the situation was normal there in the daytime, but perilous at night.
"The situation is calm during the day but scary at night," said Maher Gergous, a 53-year-old resident of the Bab al-Quba district in Hama. "Masked gunmen ... roam the streets. There are kidnappings on public roads. You will not see anyone [on the streets] after six."
A ceasefire brokered by former UN Secretary-General Kofi Annan, the joint UN-Arab League envoy to Syria, has led to a reduction in daily violence, mostly in cities where the monitors have been deployed permanently.
Syria's uprising began in March 2011 with peaceful demonstrations inspired by a wave of Arab revolts against long-ruling autocratic leaders, but it has become increasingly militarised in response to a violent government crackdown.
The UN says more than 9,000 people have died in the crackdown, while the Syrian government says it has lost at least 2,600 of its forces to "foreign-backed terrorists".
The SOHR says more than 600 people, including government troops and members of the armed opposition, have died since the truce went into effect.