Security forces opened fire as thousands of anti-government protesters took to Syria's streets in a weekly ritual of defiance and demands for Syrian President Bashar al-Assad's ousting.
Activists said at least 15 people were killed and many more injured in demonstrations following Friday prayers.
People had barely come out of Ibn Affan Mosque in the Damascus suburb of Al Qusweh, chanting for a toppling of the regime when security forces, apparently without warning, opened fire on the crowd killing, six people and wounding 15, Mohammed Suliman, a human rights activist, told Al Jazeera.
Suliman said that ambulances drove the wounded to the headquarters of the military secret service, rather than the hospital.
"We have protested peacefully in Al Qusweh for three months and now we are being accused of having gangsters among us - but we have none.
"We don't regard the president as legitimate," said Suliman, rejecting a speech made by Assad on Monday in which he announced a general amnesty for those involved in protests.
"His speech didn't make any sense. He gave his speech on Monday and today we witnessed many killed - the only speech now that will make any sense is his resignation speech."
Al Jazeera is unable to verify reports from Syria because of restrictions on reporting in the country.
More deaths occurred in the central city of Homs, according to Omar Idilbi of the Local Co-ordination Committees which track the Syrian protests.
"Our revolution is strong! Assad has lost legitimacy!" protesters chanted in the Damascus suburb of Zabadani, according to video posted on YouTube.
A huge demonstration was held in the central city of Hama, with activists saying as many as 200,000 people were taking part.
Around 5,000 people were demonstrating in Zabadani despite a heavy security presence, an activist told Al Jazeera. The protesters were singing the Syrian national anthem and calling for the toppling of the regime.
The military crackdown, which activists say has killed 1,400 people, has failed to silence a pro-democracy movement that has now lasted more than 100 days.
In northern Syria, activists said at least 15,000 people held a protest on the highway linking the country's two main cities, Damascus and Aleppo.
'Strong security presence'
Thousands marched in Amouda and Qamishli in the northeast and in other provinces, Mustafa Osso, a Syria-based human rights activist, said.
Dissidents reported a strong security presence in many locations. In Homs, all roads leading to the city centre were reported blocked.
Protesters in Damascus also carried a banner that read, "Oh germs and rats of the world, unite," taking up terms used by Assad, who likened some of Syria's troubles to a "germ" to be fought off, and Libyan leader Muammar Gaddafi, who described his country's protesters as rats.
The Syrian government blames foreign conspirators and thugs for the unrest, but protesters deny any foreign influence in their movement.
The protests, which have occurred every Friday after weekly Muslim prayers, come as Syrian refugees stream across the border into Turkey to escape a military sweep in Syria's northwest.
More than 1,500 Syrian refugees crossed into neighbouring Turkey on Thursday alone, boosting the number sheltered in Turkey to more than 11,700.
International condemnation of Syria's government has been mounting steadily in recent weeks.
The European Union on Friday extended sanctions against those supporting the government crackdown, including three members of Iran's Revolutionary Guard.
Hillary Clinton, the US secretary of state, on Thursday warned Damascus to pull its troops back from the Turkish border, where concerns grew of possible confrontations with Turkish troops.
Anticipating an exodus from Syria's second city, Aleppo, Turkish officials were setting up a sixth camp with up to 800 tents near a border crossing.
Turkish foreign minister Davutoglu told reporters on Friday he had conveyed Turkey's "concerns and thoughts" about the situation at the border in a telephone conversation with his Syrian counterpart.
He said he would continue to talk to Syrian officials to ensure that "reforms and peace are brought about as soon as possible".
"We hope that Syria is successful in renewing itself in a stable manner and comes out of the situation stronger. We will do all that we can to help," he said.