Syrian forces opened fire with live ammunition on demonstrators in Damascus overnight, wounding at least four, activists said early on Tuesday as unrest continued to spread in the capital.
Demonstrations and clashes with security forces have hit Damascus in the past week, undermining President Bashar al-Assad's argument that an 11-month uprising has been the work of saboteurs and limited mainly to the provinces.
International diplomacy showed no sign of finding a solution, as Western powers and the Arab League prepared a meeting of "Friends of Syria" on Friday to pressure Assad to step down, while Russia and China backed Assad's reform plans, derided by Syria's opposition.
"There were hundreds of demonstrators at the main square of Hajar al-Aswad (neighbourhood), and suddenly buses of security police and shabbiha (pro-Assad militia) turned up and started firing into the crowd," activist Abu Abdallah told Reuters by telephone.
He said the four wounded were taken to be treated in homes.
Footage posted on YouTube, purportedly taken before the shooting, showed a crowd marching in Hajar al-Aswad carrying placards in support of the besieged city of Homs and singing "Eyes are shedding tears for the martyrs among Syria's youth".
Elsewhere, an activists' group in Kfar Tkharim near the Turkish border said rebels had killed five soldiers and captured two in an ambush on a government column.
Opposition activists said five people had been killed in government shelling of Homs's Baba Amro district on Monday, adding to a reported death toll of several hundred since the operation began there on Feb. 3.
And activists in the western city of Hama said troops, police and militias had set up dozens of roadblocks, cutting neighbourhoods off from each other.