Tens of thousands of Syrians poured into the nation's streets today for anti-government protests, activists said, in the first major test of a fragile UN-brokered truce.
Security forces used live fire, tear gas and beat some protesters, but there was no immediate sign of widescale shelling, sniper attacks or other potential violations of the ceasefire.
However, at least three protesters were shot dead by security forces, activists said.
President Bashar Assad's regime has cracked down on protest rallies in the past and earlier suggested it would not allow them to resume today, insisting protesters needed to seek permission first.
Syrian forces tightened security in public squares and outside mosques.
A major outbreak of violence at a chaotic 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 towards civil war.
The truce is at the centre of international envoy Kofi Annan's six-point plan to stop the bloodshed and launch talks on a political transition. A 13-month uprising against Assad had become increasingly violent in response to his brutal crackdown.
Mr Annan's spokesman said the plan had been "relatively respected" despite the continued presence of government troops and heavy weapons in population centres. Ahmad Fawzi said an advance team of UN observers is poised to enter Syria if the Security Council gives the green light later today.
French president Nicholas Sarkozy said the Syrian regime must be closely monitored. "I don't believe Bashar Assad is sincere," he told French television station i-Tele. "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 today, Syrian troops fought with rebels near the border with Turkey, and other scattered violence was reported.
Tight security measures, including widespread deployment of plain-clothes 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," Mr al-Shami said.
The Britain-based Syrian Observatory for Human Rights estimated that tens of thousands of protesters calling for Assad's removal marched in cities and towns across Syria.
The Observatory said one marcher was killed in the opposition stronghold of Hama as he and others tried to reach the main Assi Square, which protesters 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, another activist group, said that across Syria, at least seven protesters were killed by troops today. It was impossible to confirm casualty tolls because the country is largely sealed off from journalists.
In Damascus, troops and pro-government militiamen known as Shabiha 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 tear gas at marchers gathering outside the Grand Mosque, the group said.
Fadi al-Yassin, an activist who took part in a protest in a town in the northern province of Idlib, said about 6,000 people participated, including women and children. Protesters dispersed peacefully after the march and troops did not open fire at them, said Mr al-Yassin, who did not want to name the location, for fear of government reprisals.
The truce, the first brokered by the international community since the Syria crisis erupted in March 2011, calls for the Syrian government to allow peaceful protests.
The Syrian government has broken promises in the past and so far ignored a key provision of Mr Annan's plan to pull troops back to barracks. Opposition leaders say Assad doesn't want to ease the clampdown because that would unleash protesters to flood the streets and escalate the movement to bring down the president.