AMMAN The United States and European Union called on Syrian President Bashar al-Assad to step down on Thursday and President Barack Obama accused him of "torturing and slaughtering" his people in what U.N. officials said would be crimes against humanity.
It was a dramatic sharpening of international rhetoric -- major states had urged Assad to reform rather than resign.
But with no threat of Western military action like that against Libya's Muammar Gaddafi, the five-month-old conflict between Assad and his opponents seems likely to grind on in the streets.
Putting faith in sanctions rather than force, Obama ordered Syrian government assets in the United States frozen, banned U.S. citizens from operating in or investing in Syria and prohibited U.S. imports of Syrian oil products.
Though U.N. Secretary-General Ban Ki-moon said Assad had assured him Wednesday that military operations were over, activists said Syrian forces carried out further raids in Deir al-Zor and surrounded a mosque in Latakia Thursday.
"The future of Syria must be determined by its people, but President Bashar al-Assad is standing in their way," Obama said. "His calls for dialogue and reform have rung hollow while he is imprisoning, torturing and slaughtering his own people."
In a coordinated move, European Union foreign policy chief Catherine Ashton called on Assad to step aside and said the EU was preparing to broaden sanctions against Syria.
At the United Nations, Britain, France, Portugal and Germany said they would begin drafting a Security Council sanctions resolution on Syria. "We believe that the time has come for the council to take further action," Britain's Deputy U.N. Ambassador Philip Parham told reporters.
U.N. human rights investigators said Assad's forces had carried out systematic attacks on civilians, often opening fire at close range and without warning, and committing violations that may amount to crimes against humanity.
A U.N. report recounted complaints of indiscriminate shooting and of wounded people being put to death with knives or by being dumped in the refrigerated rooms of hospital morgues.
In a telephone call with Assad Wednesday U.N. Secretary General Ban joined a chorus of condemnation, expressing alarm at reports of widespread violations of human rights and excessive use of force by security forces against civilians.
The Syrian Revolution Coordinating Union, an activists' group, said security forces fired machineguns near a mosque in Latakia which was surrounded by armored vehicles.
It also said Assad's forces killed at least one man when they fired live ammunition to stop residents from marching after Ramadan prayers, known as tarawih, in the Mureijeh neighborhood of Homs, 165 km (100 miles) north of the capital Damascus.
Separately, it said security forces shot dead a man it identified as Ali al-Hussein and wounded six when they fired at a sit-in in the town of al-Ruhaibeh northeast of Damascus.
Similar attacks occurred in the Houla Plain north of Homs and in the town of Qusair on the Lebanese border to the southwest, but there were no immediate reports of casualties.
U.S. Secretary of State Hillary Clinton said Assad responded to protests with "empty promises and horrific violence."
Nadim Shehadi of London's Chatham House think-tank said the shift in tone from Washington and Europe was significant, since it may give heart to Syrians who saw previous calls for Assad to reform as an indication of support for him, albeit ambiguous.
"The previous messages from the West to Bashar al-Assad were ambiguous," Shehadi said. "Now the West has hit at the very basis of the idea of his power, by telling him that we don't believe in you any more and you should leave.
Rosemary Hollis, Middle East politics lecturer at London's City University, said the move could embolden the opposition.
"It will at least send a signal to the opposition that the West is not going to save him in the face of their opposition. I think it will rattle the regime, they will feel very isolated."
It may take time, however, for the diplomatic broadside, backed by the new sanctions, to have an impact on the 45-year-old president who took power when his father President Hafez al-Assad died 11 years ago after three decades in office.
He has so far brushed off international pressure and survived years of U.S. and European isolation following the 2005 assassination of Lebanese statesman Rafik al-Hariri, a killing many Western nations held Damascus responsible for.
Despite the escalating international rhetoric and Western sanctions, no country is proposing to take the kind of military action NATO forces launched in Libya to support rebels fighting Gaddafi. That action has helped rebels take much of the country.
However, Syria's economy, already hit by a collapse in tourism revenue, could be further damaged by Obama's announcement. U.S. sanctions will make it very difficult for banks to finance transactions involving Syrian oil exports.
It will make it also challenging for companies with a large U.S. presence, such as Shell, to continue producing crude in Syria -- although the impact on global oil markets from a potential shutdown of Syria's 380,000 barrels per day oil industry would be relatively small compared to that of Libya.
Assad says the protests are a foreign conspiracy to divide Syria and pledged last week his army would "not relent in pursuing terrorist groups."
Syria has expelled most independent media since the unrest began, making it difficult to verify reports from the country.
The U.N. investigators said Syrian forces had fired on peaceful protesters throughout the country, often at short range and without warning, killing at least 1,900 civilians, including children. Their wounds were "consistent with an apparent shoot-to-kill policy," their report said.
Some were reported to have been finished off with knives.
"The mission found a pattern of human rights violations that constitutes widespread or systematic attacks against the civilian population, which may amount to crimes against humanity," it said, specifically citing the Rome Statutes of the International Criminal Court (ICC).
There was a "clear pattern of snipers shooting at demonstrators," and in some cases targeting people trying to evacuate the wounded. In hospitals "there were several reports of security forces killing injured victims by putting them alive in refrigerators in hospital morgues."
The United Nations also plans to send a team to Syria this weekend to assess the humanitarian situation there, a U.N. official said Thursday.
U.N. human rights chief Navi Pillay will address the 15-nation U.N. Security Council in a closed-door session on Syria Thursday, along with U.N. humanitarian chief Valerie Amos.
"OHCHR (Pillay's office) have indicated that their Syria report will find evidence that Syria has committed grave violations of international human rights law in its actions dealing with protesters over the past five months," a diplomat told Reuters on condition of anonymity.
Pillay also will say an international investigation is needed and she was likely to suggest the ICC war crimes court in The Hague would be appropriate, the diplomat said.
(Additional reporting by Arshad Mohammed and Deborah Charles in Washington, Justyna Pawlak in Brussels, Mohammed Abbas in London, Mariam Karouny in Beirut and Louis Charbonneau at the United Nations; Writing by Dominic Evans; Editing by Maria Golovnina)