Security forces reacted with gunfire, killing at least 10 people, seven of them in Homs, where "more than 200,000 demonstrators came out in several neighbourhoods of the city after Friday prayers," the group said.
Demonstrators also took to the streets of Damascus and the protest hubs of Daraa, Deir Ezzor and Hama, according to the Local Coordination Committees (LCC), which organises the protests.
Organisers had urged protesters to press the 22-member Arab bloc over its postponement of the emergency foreign ministers' meeting to give more time for Damascus to agree to a deal to end the bloodshed to avoid sanctions.
They had set the slogan for the protests as: "The Arab League is killing us -- enough deadlines."
On November 27, the Arab bloc approved a package of sanctions against Damascus after it failed to meet a deadline to agree to an observer mission to monitor implementation of an Arab plan to protect Syrian civilians.
But earlier this month, Foreign Minister Walid Muallem told the Arab League Syria would accept monitors under certain conditions, including the lifting of the sanctions.
The bloc's number two Ahmed Ben Helli said that Saturday's planned meeting had been postponed indefinitely while talks continued with Damascus on its offer.
However, a League task force chaired by Qatar will gather in Doha on Saturday with delegates from Egypt, Algeria, Sudan and Oman, Ben Helli said.
In Tunis, some 200 members of the opposition Syrian National Council opened a three-day congress to hone a strategy aimed at toppling the regime of Assad, with talks being held behind closed doors.
SNC chief Burhan Ghaliun said Assad's ouster was inevitable and insisted that the opposition close ranks.
"We need to emerge from this congress with a higher level of organisation, clearer targets and more momentum," he said.
The opposition has been pushing the Security Council to take tough action against Damascus after Russia and China blocked a European draft in October that would have threatened "targeted measures" against regime figures.
But Russia surprised the international community on Thursday by circulating a draft resolution.
The text condemns violence by "all parties, including disproportionate use of force by Syrian authorities" but does not squarely blame the regime for the bloodletting nor call for sanctions against Syria.
"There's unfortunately a seeming parity (in the resolution) between the government and peaceful protesters," remarked US Secretary of State Hillary Clinton.
US Defense Secretary Leon Panetta welcomed the Russian move but said after talks Friday in Ankara with Turkish leaders: "There's a lot to be worked through."
French UN Ambassador Gerard Araud called the Russian text a "manoeuvre" and said it was "totally unbalanced" but stressed that Western powers wanted to negotiate with Moscow.
Russia envoy Vitaly Churkin said his delegation would not be calling for negotiations before Monday.
His remarks came as Russian news agencies quoted a Kremlin source as saying Syrian Vice President Faruq al-Shara would meet officials in Moscow in a bid to defuse the crisis.
"He is to be received in Moscow for a serious conversation," said the unidentified source, adding that "anyone who thinks we are going to praise the vice president of Syria or pat him on the head is wrong."
Analysts said Russia may have shifted tactics but not its policy on Syria.
"Russia's position on Syria -- that there is no need to topple Assad as without him things would be even worse -- has not changed," said Alexei Malashenko, a political analyst with the Carnegie Moscow Centre.
Meanwhile, Tunisian President Moncef Marzouki told France 24 he opposes foreign intervention in Syria -- reflecting the position of Russia and China who oppose Libya-style military intervention.
And the head of Libya's National Transitional Council, Mustafa Abdel Jalil, urged Assad to step down and let the Syrian people "choose their destiny."
Meanwhile, the UN refugee agency UNHCR said more than 4,500 Syrians have fled the violence at home and found shelter across the border in Lebanon since mid-March.
The United Nations estimates that more than 5,000 people have been killed in the regime's crackdown.
----------------------------------------------------------------------------------------------------