Syria's army resumed heavy shelling of the protest hubs of Homs and Hama on Saturday, monitors reported, as international envoy Kofi Annan arrived in Russia in the latest push for peace.
Mortar rounds rained down on the flashpoint central city of Homs and nearby town of Qusayr from early morning, killing at least seven people, said the Syrian Observatory for Human Rights.
At least 14 people were reported killed in trouble nationwide on Saturday. Among them were four members of the security forces.
In the central province of Hama, the town of Qalaat al-Madiq, which the military has been trying to take for two weeks, also came under mortar bombardment and heavy machinegun fire, said the Britain-based monitoring group.
Activists reported fierce overnight clashes between troops and mutinous soldiers in and around the capital, after a day of protests under the rallying cry "Damascus, here we come."
YouTube videos showed a huge night-time demonstration in Kfar Sousa district and others in several parts of Syria's second city of Aleppo in the north.
The clashes in Damascus province were "very violent" with explosions heard across the region, including districts of the city itself, Mohammed al-Shami, an opposition activist in the capital, told AFP.
Security forces shot dead two civilians in the northwestern region of Idlib and another was killed in southern Daraa province, said the Observatory.
It was in Daraa that the revolt against the regime of President Bashar al-Assad first broke out in mid-March last year. Since then, at least 9,100 people have been killed, according to estimates by monitors.
The regime blames the violence on "armed terrorist groups."
The latest bloodshed came as UN-Arab League envoy Annan arrived in Moscow to gauge how far Russia is willing to push its key Arab ally after it finally joined a UN call on regime forces to pull back from protest cities.
Annan will meet President Dmitry Medvedev and Foreign Minister Sergei Lavrov on Sunday.
He will also visit China, the other UN Security Council member resisting global efforts to condemn Assad, on Tuesday and Wednesday, the foreign ministry in Beijing said. He had been expected to head there on Sunday.
The special envoy is carrying with him Assad's answer to a peace plan under which Syria could begin a "political transition" to a representative government, with no specifically defined role for the Syrian leader.
Moscow backed Wednesday's non-binding Security Council statement in support of the initiative only after making sure it contained no implicit threat of further action should Assad fail to comply.
Washington's UN ambassador Susan Rice admitted the UN call represented only "a modest step" towards ending the conflict.
But it came amid growing signs that Moscow was beginning to lose patience with Assad, despite his commitment to massive new Russian arms purchases and the granting of key naval access to the Mediterranean Sea.
A top Kremlin-linked lawmaker said Assad should treat the UN statement as "an insistent recommendation" whose implementation would determine the future course of relations between the two countries.
"Assad has to take the first step: he must pull the Syrian army out of large cities," the lower house of parliament's foreign affairs chief Mikhail Margelov said on Thursday.
"Russia's future position on the conflict will depend on how successfully (the Syrian government) complies with the provisions spelled out in the Security Council statement," Margelov said.
But analysts have warned that Russian interests in Syria are too important for it to allow Western and regional powers to independently dictate the battle-scarred nation's fate.
Russia not only sells billions of dollars in arms to Syria but also relies on Damascus to lobby its interests in a region where Moscow has lost much of its influence in recent years.
On Friday, the European Union agreed an assets freeze and travel ban on "Assad's wife, mother, sister and sister-in-law," and eight other entourage members, diplomats said.
Asma Assad, whose parents live in Britain where she grew up, cannot be barred entry to the country but is not expected "to try to travel to the United Kingdom at the moment," British Foreign Secretary William Hague said.
Assad himself was targeted in May last year, along with his younger brother Maher.
Washington welcomed the EU decision.
"We are gratified that the EU has taken yet another step in tightening the noose on the Assad regime," US State Department spokeswoman Victoria Nuland said.
Adding to the pressure, at least four brigadier generals defected in recent weeks, experts told a UN rights commission, saying this showed a growing number of ranking officials are abandoning Assad's regime.