(CNN) -- An explosion at a car wash near Syria's largest city of Aleppo killed at least five people Saturday, opposition activists said.
The blast occurred as security forces drove by in a bus, but it was unclear whether the fatalities were soldiers or civilians, according to the Britain-based opposition Syrian Observatory for Human Rights.
In the capital of Damascus, two separate blasts, including one targeting a military vehicle, left three government soldiers injured, according to the group.
The new attacks came after violence flared at the sprawling Aleppo University, one of several schools where anti-government protests have erupted recently. Seven were killed at the university Thursday.
Aleppo, a bastion of support for al-Assad, has been largely spared in Syria's 14 months of bloody uprising. Recent protests there could signal a significant shift.
Aleppo's Christian minority and community of businessmen and merchants don't want to see the regime fall, said Andrew Tabler, a Syria expert who is a fellow at the Washington Institute for Near East Policy.
"The regime is very worried," he said. "Their actions in the last few days demonstrate that."
At least 25 people were killed across the nation Saturday, the opposition Local Coordination Committees of Syria said.
CNN cannot independently verify reports of violence and deaths within Syria because the government has restricted access by most of the international media.
In the opposition stronghold of Homs, Syrian forces shelled a crowded neighborhood at dawn, killing two police defectors.
The state-run Syrian Arab News Agency (SANA), meanwhile, said 265 detained men, who were "involved in events" but committed no crimes, were freed Saturday.
As the violence raged, the head of the opposition political group, the Syrian National Council, was expected to arrive in China for talks Sunday.
Burhan Ghalioun will meet Foreign Ministry officials during his trip, state-run Xinhua news agency reported.
Earlier this year, China and Russia derailed a U.N. Security Council resolution demanding an end to attacks on peaceful protesters.
The latest attacks, in violation of a peace plan brokered by international envoy Kofi Annan, escalated doubts as to whether the violent 14-month uprising can be resolved.
A spokesman for Annan said it will take time for the plan to take hold.
"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," spokesman Ahmed Fawzi said Friday. "Sadly, time is a luxury that we don't have. But realistically, it's going to take a little more time to pull all the strings together, but rest assured that they are being pulled together."
While there are no big signs of compliance with the plan, he said, there are small signs such as some heavy weapons have been withdrawn and violence has receded.
The head of the U.N. mission in Syria, Gen. Robert Mood, said the government is allowing observers access and the team has seen more commitment to the cease-fire plan.
Dozens of unarmed military observers are in Syria with a total of 300 expected in the country by the end of the month to monitor the cease-fire and the peace plan.
Video posted to YouTube on Sunday purported to show U.N. monitors meeting with Free Syrian Army (FSA) opposition forces in the city of Busra, in Daraa province.
In the video, which CNN could not independently confirm, a member of the FSA tells the monitors the opposition is complying with the cease-fire and hopes that the other side will too.
"There is gunfire and shelling everyday ... Of course, this happens after you leave the city you were visiting," he said.
The cease-fire went into effect April 12 and is part of a six-point peace plan negotiated by Annan.
The plan includes the government allowing humanitarian groups access to the population, releasing detainees, starting a political dialogue and withdrawing troops from city centers.
Syria's protests started peacefully in March of last year, but a government crackdown spawned violence that has left thousands dead and prompted some military defectors to take up arms against the regime forces. The government has consistently blamed the violence on "armed terrorists."
The United Nations estimates that at least 9,000 people have died in the conflict but that estimate is old and believed low by opposition groups.
CNN's Hamdi Alkhshali, Amir Ahmed and Moni Basu contributed to this report.