Barack Obama, the US president, has said Syria's deadly crackdown on protesters "must come to an end now" and accused Damascus of seeking Iranian help to repress its people.
Some 75 protesters were killed on Friday, according to human rights group Amnesty International, in the bloodiest violence in a month of escalating protests against Syrian president Bashar al-Assad's rule.
Local activists have released a list of 103 people who they say were killed in Friday's crackdown. SANA, the official news agency, put the number of people killed on Friday at 10, reporting that they died in clashes between protesters and passers-by. The SANA account said that security forces only used tear gas and water cannons.
"This outrageous use of violence to quell protests must come to an end now," said Obama on Friday, dismissing as "not serious" Assad's lifting of a decades-old emergency law in Syria this week and accused him of seeking help from Iran.
"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," he said.
"We strongly oppose the Syrian government's treatment of its citizens and we continue to oppose its continued destabilising behaviour more generally, including support for terrorism and terrorist groups," said Obama.
Despite the criticism, Obama did not refer to any potential US consequences should Assad refuse to heed his demands.
UN demands 'independent' investigation
Ban Ki-moon, the UN secretary-general, meanwhile, has condemned the Syrian government's killing of demonstrators, calling for an "independent, transparent and effective investigation into the killings", his spokesman said on Friday.
"The secretary-general condemns the ongoing violence against peaceful demonstrators in Syria, which again has killed and injured many today, and calls for it to stop immediately," Farhan Haq, Ban's spokesman, said from the UN headquarters in New York.
Ban said that President Assad's government must "respect international human rights, including the right to freedom of expression and peaceful assembly, as well as the freedom of the press".
The UN secretary-general stressed that "only an inclusive dialogue and the effective implementation of reforms can address the legitimate aspirations of the Syrian people and ensure social peace and order".
Jerzy Buzek, the European Parliament chief on Friday also condemned the shooting deaths of protesters in Syria and called for the release of all prisoners of conscience.
"Today's violent crackdown on peaceful demonstrations all over Syria is unacceptable. The bloodshed has to stop now: this is the government's first and foremost responsibility," he said in a statement.
"Any form of violence against peaceful demonstrators must stop: no more killing, no more torture, no more arbitrary arrests. An independent investigation into the deaths of protesters has to be carried out."
France also urged Syrian authorities to halt their use of violence on anti-government protesters.
"We call on them once more to engage in an inclusive political dialogue without delay and to put into place reforms that respond to the legitimate aspirations of the Syrian people," said deputy spokeswoman Christine Fages, deputy spokeswoman for the foreign ministry.
She also called for the release of those arrested and for respecting basic rights, including media freedom and the right to hold peaceful demonstrations.
Peak of violence
At least 75 people were killed on Friday as security forces use live ammunition and tear gas to quell anti-government protests across the country, according to human rights group Amnesty International.
Friday's death toll was one of the bloodiest in protests for democratic change - the first since emergency rule was imposed by the ruling Baath Party when it seized power in 1963.
Amnesty International called for an immediate end to the attacks on protesters and for an investigation into the deadly events.
"The Syrian authorities have again responded to peaceful calls for change with bullets and batons," said Malcolm Smart, the London-based organisation's director for the Middle East.
"They must immediately halt their attacks on peaceful protesters and instead allow Syrians to gather freely, as international law demands."