Thousands of Syrians have taken part in protests against President Bashar al-Assad's regime testing a shaky UN ceasefire, as state media said 18 security personnel were killed in attacks.
The latest violence came as peace envoy Kofi Annan acknowledged the situation was "not good" and as rights monitors reported at least 14 civilians were also killed.
"It's a very fragile ceasefire," Mr Annan’s spokesman Ahmad Fawzi told reporters of the tenuous truce which has seen more than 150 civilians killed since it went into effect on 12 April.
A deadly blast took place in the southern region of Quneitra, near the demarcation line with Israel on the Golan Heights, killing 10 members of the security forces, state television said, blaming an "armed terrorist group."
Official news agency SANA said the bomb was detonated by remote control and targeted a bus transporting troops.
Reports from Syria cannot be independently verified as state authorities have barred international journalists and rights groups.
State media said a similar bomb attack in Karak, in southern Daraa province, killed five soldiers, adding that another three were killed in separate incidents elsewhere.
Thousands took to the streets across the country after Muslim weekly prayers, the Syrian Observatory for Human Rights said.
Protests took place in Daraa, the Damascus region, in Homs and Hama in central Syria, Idlib in the northwest, Aleppo in the north, Deir Ezzor in the northeast and in Latakia on the Mediterranean coast, it said.
Meanwhile, an advance team of UN military observers resumed work bolstered by the signing yesterday of a protocol governing their mission to monitor a six-point plan brokered by Mr Annan.
UN chief Ban Ki-moon urged the Security Council to take "early action" to bolster the mission, while acknowledging that boosting its numbers to 300 was "not a decision without risk."
Opposition activists had called for a show of defiance against Assad's regime for the main weekly protests.
Across the country, activists reported a massive security force presence, particularly outside mosques, the traditional starting point for marches and protests.
French Foreign Minister Alain Juppe said the UN observer mission needed to be able to guarantee Syrians the freedom to protest.
"We need observers on the ground, but properly equipped observers with helicopters that can ensure the right to protest. It's extremely important. The day this freedom is guaranteed, the regime will fall," he said.
However the head of the small observer advance team, Morocco's Colonel Ahmed Himmiche, said it would not be attending demonstrations for fear that "our presence is used for an escalation."
"Today, we have other tasks. We are going to meet civilians and representatives of organisations," Mr Himmiche told AFP as his team prepared to leave their Damascus hotel.
The advance party has visited the Daraa region but has not so far been able to visit Homs, where rebel neighbourhoods have come under repeated deadly bombardment, Ban said.
The Britain-based Syrian Observatory said that the rebel Khaldiyeh district of Homs - Syria's third-largest city - was under heavy bombardment for another day, and five civilians were killed there.
Activists in the town of Qusayr, farther north, also reported heavy bombardment, where three civilians were reported killed.
It said regime forces killed an activist in Idlib, two civilians in Damascus, one in Aleppo and another in a bomb blast in the same region.
Another was shot dead in Hait village in the southern province of Daraa, the Observatory said.
Damascus ally Moscow insisted that the ceasefire was generally holding despite violations and should be viewed as an achievement that was saving Syria from a broader civil war.
On the humanitarian front, a $180 million (€140 million) draft plan for delivering aid for Syria's one million needy has been drawn up and is awaiting the green light from Damascus, the United Nations said.
A successful assessment mission has been carried out and donors are ready with their cash to provide food, medical and other supplies, said John Ging, director of operations for the UN Office for the Coordination of Humanitarian Affairs.
