Two explosions rocked central Damascus on Saturday, a watchdog said, a day after Syrian security forces killed at least 30 civilians despite the presence of UN observers.
"One bomb exploded in As-Saura Street," an key commercial artery in the capital, while the location for the other was uncertain, Rami Abdel Rahman of the Syrian Observatory for Human Rights told AFP.
Abdel Rahman, speaking on the phone from Britain where his rights watchdog is based, accused the government of carrying out the bombings to prevent people attending funerals for nine civilians killed in Damascus on Friday.
The nine died during demonstrations and funerals in the neighbourhoods Kfar Sousa and Tadamon.
"This is the highest death toll we have seen inside Damascus" since a ceasefire took hold in April 12, added Abdel Rahman, whose group says more than 600 people have been killed nationwide during the tenuous truce.
Opposition bloc the Syrian National Council called in a statement early Saturday on the UN observers to visit Kfar Sousa and Tadamon, "where the funerals of the martyrs killed Friday will be held."
The peace agreement was brokered by UN-Arab League envoy Kofi Annan, whose office said Friday that his peace plan was "on track."
Under the six-point plan, the government of embattled President Bashar al-Assad is supposed to withdraw its troops and heavy weapons from urban areas and allow peaceful demonstrations.
On Friday, protesters emerged from mosques after weekly prayers across the country, calling for Assad's ouster, said the Syrian Observatory for Human Rights.
Among Friday's casualties were a couple and their child shot dead in the northern city of Aleppo, scene of a bloody regime raid the day before in which four university students died.
Another 200 students were arrested in what the Observatory said could prove a turning point of the uprising in Aleppo, Syria's second city and commercial hub, largely spared the violence so far.
Troops also shot at demonstrators in various other cities and towns, activists said.
Opposition activists had called for the protests under the rallying cry: "Our commitment (to the revolution) is our salvation."
Anti-regime demonstrations have been staged after prayers each Friday since the revolt against Assad's iron-fisted rule erupted in March 2011.
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An amateur video posted on YouTube by activists showed demonstrators in Irbin, a town in Damascus province, carrying a banner that read: "Dear observers, thank you for your visit and goodbye."
"One year of killings and you still need observers to know the truth? Enough lies," read another banner carried by protesters in a neighbourhood of the capital.
Overall, the Observatory estimates that more than 11,000 people have been killed since the outbreak of the revolt against Assad's regime.
Abu Omar, an activist in the Damascus region, told AFP via Skype that it was clear government troops were not intimidated by the presence of UN observers.
"The security forces seem very much at ease with the situation, as though they've been given the green light to go on with the crackdown," he said.
He added that in some regions around the capital, government checkpoints had been beefed up rather than drawn down.
Major General Robert Mood, who heads the UN mission to oversee the hard-won ceasefire agreement, had issued an appeal late Thursday for the Assad regime to make the first move to end the violence.
"The strongest party needs to make the first move," he told reporters in Syria, stressing he was referring to the government and army.
"They have the strength, they have the position and they also have the potential generosity to make the first step in a good direction," he said.
The official SANA news agency said observers on Friday visited Latakia on the coast, the northwest Idlib province, the central city of Hama and the village of Tal Kalakh near the border with Lebanon.
In Geneva, Kofi Annan's spokesman said his peace plan was "on track."
"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," Ahmad Fawzi told journalists.
"There are signs on the ground of movement, albeit slow and small.
"Some heavy weapons have been withdrawn, some heavy weapons remain. Some violence has receded, some violence continues. And that is not satisfactory, I'm not saying it is," Fawzi said.