DAMASCUS (AFP) – At least 13 mourners were shot dead on Saturday as Syrians swarmed the streets to bury scores of demonstrators killed in massive protests and two MPs resigned in frustration at the bloodshed.

Activists said the death toll from Friday's nationwide protests could top 100, pending confirmation of a list of names.

Two independent MPs from the protest hub city of Daraa, Nasser al-Hariri and Khalil al-Rifai, told Al-Jazeera television they were resigning in frustration at not being able to protect their constituents.

Daraa's top religious leader, Mufti Rizq Abdulrahman Abazeid, also quit.

Friday's deaths signalled no let-up from President Bashar al-Assad, whose forces used live ammunition against demonstrators nationwide, witnesses and activists told AFP.

The bloodshed erupted as tens of thousands of people took to the streets for "Good Friday" protests to test long sought-after freedoms a day after Assad scrapped decades of draconian emergency rule.

The Syrian Revolution 2011, a driving force behind the protests, marked the tone on Saturday by posting on its main Facebook page a black banner with the word "Mourning" in both Arabic and English.

Tens of thousands of mourners packed buses and headed for the southern town of Ezreh for the funerals of 18 people killed on Friday, a rights activist requesting anonymity told AFP by telephone.

Another activist later said "12 martyrs were buried in Ezreh" and that two men in the funeral cortege heading for the town -- Yasser Nseirat and Jamal Qanbar -- were shot dead by security forces.

Other activists spoke of five mourners killed in Ezreh and outside a hospital in Daraa, with the toll expected to rise.

Daraa has been an epicentre of protests against the regime of Assad, who also scrapped the feared state security court on Thursday and signed a decree "to regulate" peaceful protests.

Snipers also pinned down mourners in the northern Damascus suburb of Douma, killing at least five more people on Saturday, according to a witness and a human rights activist.

They opened fire from roof-tops as mourners marched from a mosque to a cemetery, the sources said, adding that tens of thousands of people took part.

Activists also reported at least three people shot dead by security forces in the Barzeh district of Damascus.

The state-run SANA news agency said two members of the security forces shot dead on Friday by "armed criminal groups" in Homs and Madamiyah near Damascus were buried on Saturday.

It said mourners affirmed "the need to preserve national unity and defend Syria's security and stability to foil the plot to harm the country."

Meanwhile, Daniel Saud, head of the Committees for the Defence of Democracy, Freedoms and Human Rights in Syria, was arrested at his home in the northwestern city of Banias, lawyer Khalil Maatouk told AFP.

"This signifies that the security services are continuing to act" as they did before the emergency law was lifted, Maatouk said.

A group called the Committee of Martyrs of 15 March Revolution issued a list of 82 names of people it said were killed on Friday, but said the toll from the "massacre" could reach 100 as it tried to confirm more deaths.

Amnesty International, citing Syrian activists, said at least 75 people were killed when the "government launched its deadliest crackdown yet on demonstrators" seeking reform.

Friday's toll compared with killings on March 23 in the southern town of Daraa, when activists said 100 people died, Amnesty said.

Officially, Syria has blamed "armed gangs" for Friday's bloodshed, and SANA said security forces intervened using only tear gas and water cannon to prevent clashes between protesters and passers-by.

Eight people were killed on Friday in Ezreh and 20 others wounded "including security forces in an attack by criminal gangs," SANA said, adding that two policemen had died in Damascus and the central city of Homs.

The crackdown drew an international outcry.

Russia, France, Germany, Italy and Greece joined the chorus of condemnation from Washington, Paris, London, Brussels and UN headquarters in New York.

US President Barack Obama blasted Syria's "outrageous" use of violence, accusing Assad's regime of seeking Iran's aid in the brutal crackdown on the pro-democracy movement that erupted in Damascus on March 15.

"Instead of listening to their own people, President Assad is blaming outsiders while seeking Iranian assistance in repressing Syria's citizens through the same brutal tactics that have been used by his Iranian allies."

But a senior official in Damascus, quoted on SANA, said Obama's condemnation was "not based on an objective vision of the reality on the ground."

Iran also denied any involvement in putting down the protests, but at the same time criticised the use of force against demonstrations, without naming Syria.

UN chief Ban Ki-moon said Assad's government must "respect international human rights" and called for an independent probe into the killings, as France urged Syria to launch a "political dialogue without delay."

Russia, the first of Syria's allies to speak out, urged Damascus to accelerate "broad-scale political, social and economic reforms," saying Moscow views Damascus as its "friend."

Thousands of protesters chanting "freedom, freedom," and calling for the fall of the regime swarmed cities across Syria on Friday from Qamishli in the northeast to Daraa, witnesses said.

Protesters have said Thursday's decrees were insufficient, insisting on the release of political prisoners and dissolution of Syria's security apparatus.