Damascus accuses US of interfering in internal affairs after Washington voices anger over attack on its embassy.
Armed men under the watch of Syrian security forces looted shops and fired on crowds in the central city of Homs, killing at least one person and wounding many others, witnesses have said.
The fresh violence on Saturday night follows what is reported to have been one of the deadliest crackdowns on protesters since the anti-government uprisings began in Syria four months ago.
“Armed thugs are randomly shooting at locals in various districts of Homs. One is reported killed and more than 20 others are injured,” Majed, a resident from Homs, told Al Jazeera.
“The thugs are looting local shops under the watch of Syrian security forces. Random shooting is still going on at the moment.”
Police also killed four people in the south near the Jordanian border on Saturday, the Reuters news agency said, quoting witnesses and activists.
Three protesters were shot dead in the northern city of Idlib, they said.
Tens of thousands of Syrians took to the streets on Saturday, shouting “we want freedom” while carrying caskets of of some of the protesters killed during protest rallies on Friday.
Activists said at least 32 people were killed when hundreds of thousands of demonstrators protested against the government of Bashar al-Assad, the president, following Friday prayers.
About 23 people were killed in Damascus, which until now had seen only scattered protests, and its suburbs – the highest death toll for the city so far, Mohammad Abdullah, a spokesman for the Local Co-ordination Committee (LCC), said on Saturday.
The LCC tracks anti-government demonstrations in the country.
Exiled Syrian dissidents met in Turkey on Saturday to urge their countrymen to launch a campaign of civil disobedience to try to force Assad from power.
At least 400 members of the opposition, comprising conservative Islamists and liberals, attended the so-called National Salvation Congress in Istanbul on Saturday to try to unite behind the goal of ending 41 years of Assad family rule.
“We want to raise the intensity of the peaceful confrontation by civil disobedience and to choke the regime
economically and paralyse the state with the least damage,” Wael al Hafez, an opposition figure, told the Istanbul gathering.
Reports from the conference suggest the different factions have struggled to agree on whether to form a shadow government.
“We will build our council here in Istanbul with some branches to help the people’s movement in the streets by money for example. And by meeting responsible people in Turkey to put pressure on the regime to stop attacking the people demonstrating on the streets,” Haytham Al Maleh, a senior opposition leader, told Al Jazeera from Istanbul.
Activists in Damascus also took part in Saturday’s meeting by telephone. Organisers had planned to hold a conference in Damascus in tandem with the Turkey meeting, but it was cancelled after Friday’s bloodshed.
Addressing the conference by phone from the capital, Mashaal Tammo, an opposition figure, said Assad had lost his legitimacy to rule and called on him to step down.
In an emotional speech, he said the “the existence of the regime was no longer justified” and called for a peaceful transition to a civil, pluralistic and democratic state.
‘Brutality has to stop’
The government crackdown has led to international condemnation and sanctions.
“What’s happening in Syria is very uncertain and troubling because many of us had hoped that President Assad would make the reforms that were necessary,” Hillary Clinton, the US secretary of state, said in Turkey on Saturday.
“The brutality has to stop, there must be a legitimate sincere effort with the opposition to try to make changes.”
Activists say the government’s crackdown on dissent has killed about 1,600 people since March, most of them unarmed protesters.
But the regime disputes the toll and blames a foreign conspiracy for the unrest, saying religious extremists-not true reform-seekers-are behind it.