The demonstrations on Friday came as the UN security council prepared to approve the dispatch of the first group of monitors to Syria. They are expected to arrive in the country as early as next week.
An advance team of UN observers is poised to enter Syria if and when the security council gives the green light for its deployment, while a larger contingent of up to 250 observers could be approved next week if the truce holds.
France called for the creation of aid corridors to help Syrians escape "massacres", saying a UN-brokered ceasefire offered an opportunity to put the humanitarian measures in place.
President Bashar al-Assad's opponents had called for mass demonstrations to test whether the authorities would tolerate a return to peaceful protests, as the joint Arab League-UN envoy Kofi Annan's six-point peace plan said they should.
But rallies videoed by activists were far smaller than the huge, chanting crowds seen in major cities at the start of the uprising 13 months ago and on several occasions in 2011.
International pressure has grown for Syria to fulfil all its commitments to the former UN chief by withdrawing troops and heavy weapons, permitting humanitarian and media access, releasing prisoners and discussing a political transition.
Instead, Syrian forces appeared to tighten security around public squares and outside mosques. According to activists whose accounts could not be independently verified, security forces used live fire, teargas and beat protesters to prevent them gathering in cities across the country. The same sources said that at least three protesters were shot dead by security forces during the day.
In the Damascus suburbs of Zabadani and Douma, and in the northern town of Idlib, large crowds linked arms and chanted anti-government slogans.
In the southern city of Deraa, birthplace of the uprising, several hundred people formed rows, holding hands and dancing to the beat of a drum while chanting, "Come on, Bashar, leave!"
The government claimed that opposition fighters had killed an officer in Hama, which would also represent a breach of the ceasefire.
However, there was no evidence of widespread shelling, sniper attacks or other potential violations of the ceasefire.
The reports of ceasefire violations – over 30, according to activists – came as Ahmad Fawzi, Annan's spokesman, said that scattered reports of violence in Syria did not mean the ceasefire was failing, and called on both sides to exercise restraint.
"With every cessation of hostilities there will be skirmishes. This is not unusual, sometimes the parties test each other," he said, adding, "The most important thing is that the guns remain silent."
"Wherever their positions, we hope they should and will remain silent."
"There may continue to be skirmishes for hours or even days, but the fact of the matter remains that heavy shelling … has died down."
It had been feared that a major outbreak of violence at a protest rally could give government forces a pretext for ending the peace plan, which aims to calm a year-old uprising that has killed 9,000 people and pushed the country toward civil war.
The holding of the fragile ceasefire into a second day – despite widespread scepticism about Assad's commitment to the peace plan – came as the French president, Nicholas Sarkozy, said the Syrian regime must be closely monitored.
"I don't believe Bashar Assad is sincere," Sarkozy told French television on Friday. "I don't believe in the ceasefire, sadly. I believe – and it's what I was discussing with Barack Obama yesterday – that at the very least, observers must be sent to find out what's happening."
Earlier on Friday, Syrian troops fought with rebels near the border with Turkey, and other scattered violence was reported.
Tight security measures, including widespread deployment of plainclothes agents of the feared mukhabarat intelligence service, prevented large-scale marches in the Syrian capital, said Damascus-based activist Maath al-Shami. He said many regime opponents chanted anti-government slogans inside mosques, but were unable to take the marches outside due to the heavy security presence.
"The big security campaign succeeded in limiting the size of the protests," Shami said.
The Syrian Observatory for Human Rights, a British-based activist group, estimated that tens of thousands of protesters calling for Assad's ouster marched in cities and towns across Syria.
The group said one marcher was killed in the opposition stronghold of Hama as he and others tried to reach the main Assi Square, which protesters had occupied for several weeks last year. Two others were killed and 11 wounded in the southern town of Nawa when protesters came under fire from security forces as they gathered in the central square, said area activist Adel al-Omari.
The grassroots Local Co-ordination Committees said that across Syria, at least seven protesters were killed by troops on Friday. It was impossible to confirm casualty tolls because the country is largely sealed off from journalists.
In Damascus, troops and pro-government shabiha militiamen surrounded a mosque in the Qadam neighbourhood and beat people staging a protest inside the house of worship, said the LCC. In another Damascus neighbourhood, Barzeh, demonstrators called for the downfall of the regime, the LCC said. In Aleppo, troops fired teargas at marchers gathering outside the Grand Mosque, the group said.
