The head of the Arab League has asked the UN Security Council to boost the size of a UN mission in Syria and give it expanded powers to protect people following a surge in violence there, according to a letter leaked to media outlets on Friday.
Images of the bloodied bodies of children and others massacred in the city of Houla in attacks blamed on President Bashar al-Assad's forces have shocked the world and highlighted the failure of a six-week-old UN-backed ceasefire plan to stop the violence in the 14-month uprising against Assad's rule.
Nabil Elaraby, secretary-general of the Arab League, condemned the attacks in a letter to the Security Council.
"I therefore urge you to move quickly to end all acts of violence taking place in Syria, and to take the necessary measures to protect Syrian civilians, including increasing the number of international monitors and allowing them the necessary powers to put a stop to the violations and crimes being committed," Elaraby said in the letter.
Elaraby, who has said the violence was intended to undercut a truce brokered by international mediator Kofi Annan that never took hold, is struggling to keep alive Annan's six-point peace plan and avert full-scale civil war in Syria.
Security Council diplomats in New York said they received the letter, although it was not immediately clear how they would react.
Calls for investigation
The latest diplomatic development came as Aleppo, Syria's second city, saw on Friday its largest protests since the country's uprising began in March 2012.
Amateur footage posted online by activists showed anti-government protesters being dispersed before they reached the city centre.
Meanwhile, the UN Human Rights Council has condemned Syria for last week's massacre in the Houla region and called for a UN investigation to identify the perpetrators and gather evidence for possible criminal prosecution.
The 47-member forum, which held an emergency session in Geneva, adopted a resolution on Friday by a vote of 41 states in favour to three against - China, Cuba and Russia - with two abstentions and one delegation absent.
The resolution was put forward by Qatar, Turkey and the US amid international outrage at the killing of 108 people, nearly half of them children, in Houla a week ago.
Speaking to Al Jazeera from Geneva, Laura Dupuy Lasserre, the permanent representative of Uruguay to the UN and also the president of the Human Rights Council, said the council holds the Syrian government responsible for the violence in Houla.
"The council in its resolution understands that pro-regime elements and Syrian govenrment artillery and tank shelling were used against residential neighbourhoods. That means: attacking the civilian population," Dupuy Lasserre said.
"Nevertheless, it reiterates that all violence in all its forms by all parties must seize as well."
The 193-nation UN General Assembly is planning to meet next Thursday to discuss the escalating crisis in Syria and the Houla massacre.
International mediator Kofi Annan and Navi Pillay, the UN High Commissioner for Human Rights, are expected to address the assembly, UN diplomats told the Reuters news agency.
Annan will also speak to the 15-nation UN Security Council that day about the lack of progress implementing his six-point peace plan.
Syria's delegation at the Human Rights Council accused "terrorists" of carrying out the killings - its term for anti-government fighters - and rejected the text as politically motivated interference.
It said its own investigation was under way.
"The perpetrators will be brought to the courts and will not go unpunished," Syrian diplomat Tamim Madani told the meeting before the vote.
In-depth coverage of escalating violence across Syria
"Voting for this resolution is tantamount to killing the victims again."
Pillay said Syrian forces and pro-government armed men accused of committing the slaughter could face prosecution for crimes against humanity, in a speech read out on her behalf.
She again called for the Security Council to refer Syria to the prosecutor of the International Criminal Court.
But Russia and China, which dismissed the text as "unbalanced", said that UN observers were already investigating the massacre and there was no need for duplication.
Vladimir Putin, the Russian president, warned on Friday of an "extremely dangerous" situation in Syria but rejected military intervention as he met with Angela Merkel, the German chancellor, in Berlin.
Hours later, in a joint press conference with French President Francois Hollande, Putin said "sanctions hardly ever work in an efficient manner" and indicating that Assad's departure would not in itself resolve the crisis.
"What is happening in Libya? What is happening in Iraq? Has it become safer there?" he said in Paris. "We propose to act in an accurate, balanced manner at least in Syria."
But Hollande kept up the pressure for decisive action, insisting that Assad's departure was "a prerequisite for a political transition" and that "there must be sanctions" against his regime.
"Bashar al-Assad's regime has conducted itself in an unacceptable and intolerable manner. It has committed acts that disqualify itself" from governing, said Hollande.