Syrian security forces on Friday killed 18 people in pro-democracy protests, according to the opposition, as a human rights group accused government troops of committing "crimes against humanity", dpa reported.
Thirteen deaths were reported in the central cities of Homs and Hama, four in the southern province of Daraa, and one in Idlib near the border with Turkey, London-based activist Omar Idlibi told dpa.
"Two of the dead were army deserters who were found shot in the head near a garbage dump in Homs," he said.
Opponents of the regime on Friday held mass protests in several parts of the country, demanding that the Arab League suspend Syria's membership.
The pan-Arab organization is to hold emergency talks Saturday in Cairo to discuss the situation in Syria.
Human Rights Watch (HRW) Friday accused Syrian government forces of committing "crimes against humanity," including torture, killings and forced disappearances in Homs.
Homs has emerged as the most restive area in Syria since the anti-government protests erupted in March.
"Homs is a microcosm of the Syrian government's brutality," said Sarah Leah Whitson, HRW's Middle East director.
The New York-based group added in a report that apart from rampant torture and the killings, it had found evidence of arbitrary arrests, and that several hundred people remain missing.
The report was based on 110 interviews with victims and witnesses from Homs city and the province of the same name, and focused on violations committed from mid-April to end-August.
In that period, government troops killed at least 587 civilians in Homs - the highest number for any province, said HRW.
More than 3,500 people have been killed in Syria since the protests began in mid-March, according to the United Nations.
On Friday, the chief of the Lebanese Hezbollah movement, Hassan Nasrallah, warned that an attack by Western powers on Syria will develop into a regional war.
"The United States must understand that war on Iran and Syria will not remain in these two countries but will spread to other countries in the region," said Nasrallah, whose party is backed by Tehran and Damascus.
"We are not issuing any threats, but this is the reality," he told a rally in Beirut's southern suburbs.
Meanwhile, a delegation from the opposition Syrian National Council was to visit Moscow on the invitation of the Russian government, a key ally of Syrian President Bashar al-Assad.
The council, which includes mainly Syrian opposition figures living outside the country, "will visit Moscow after being officially invited by the Russian government," Russia's deputy minister of foreign affairs, Mikhail Bogdanov, told the website NOW Lebanon.
They group will discuss "the ways to resolve the crisis in Syria," with officials in Russia, which vetoed a UN Security Council resolution condemning al-Assad's government for its crackdown on protesters.