Activists said four people -- a couple and their young child and a 16-year-old -- were killed Friday in Aleppo, Syria's largest city, The New York Times reported.
The protesters in Aleppo were demonstrating against the closingThursday of the 60,000-student Aleppo University by security forces.
At least four students were killed in the violent closing, including one who was allegedly thrown from the window of a high-rise dormitory.
Syrian President Bashar Assad had continued to receive support in Aleppo while losing support in other cities, the Times said.
The firing on civilians in Aleppo violated the cease-fire brokered by the United Nations and the Arab League and showed Assad does not plan to abide by the cease-fire plan, analysts said.
"This proves that [the Assad regime is] not about to allow that kind of assembly in the future," said Andrew J. Tabler, a fellow at the Washington Institute for Near East Policy and an expert on Syria. The Assad government, he said, viewed Aleppo to be "one of the trigger cities. They're very scared about Aleppo. That's a real weakness for them."
The Times said the number of daily deaths appears to have declined since the cease-fire took effect in mid-April.
The United Nations has about 50 cease-fire monitors in Syria and plans to send up to 300 by the end of the year.
The cease-fire will take time to take hold, Ahmad Fawzi, a spokesman for Kofi Annan, the special envoy who negotiated the plan, said Friday.
"The Annan plan is on track, and a crisis that has been going on for over a year is not going to be resolved in a day or a week," he said.