The United States has imposed new sanctions on Syria over its brutal repression of mass protests, and again claimed that Iran's Revolutionary Guard was aiding the crackdown.
Europe also imposed an arms embargo and considered additional sanctions against Bashar Al-Assad's government, hardening the international front against Damascus on another day of bloody violence in Syria.
US President Barack Obama's asset freezes and restrictions on financial transactions notably targeted Maher Al-Assad, the powerful brother of the president, who commands Syria's feared Fourth Armored Division.
Also named in Obama's executive order enshrining the sanctions were Ali Mamluk, director of Syria's Intelligence Directorate, and Atif Najib, the ex-head of intelligence in Daraa province, the epicenter of political violence.
The Syrian intelligence directorate as a whole was also targeted by the sanctions, which came after US calls for restraint in Syria went unheeded and as Obama faced increased pressure for a more robust response.
"The United States strongly condemns the Syrian government's continued use of violence and intimidation against the Syrian people," the White House said in a statement Friday.
"We call upon the Syrian regime and its supporters to refrain from further acts of violence and other human rights abuses against Syrian citizens seeking to express their political aspirations."
The statement also singled out Iran's Revolutionary Guards, saying the Corps was acting as a conduit for material support for the Syrian government which was helping it enforce the crackdown.
"Iran's actions in support of the Syrian regime place it in stark opposition to the will of the Syrian people," the White House said.
The Revolutionary Guards have previously been sanctioned by Washington for providing support to terrorism.
The new measures block any property in the United States or in the possession or control of Americans belonging to the named individuals and entities and prevents them entering transactions with US individuals.
State Department Policy Planning Director Jacob J. Sullivan said that Washington was specifically targeting individuals and entities it believed responsible for violence.'
"If they continue this violence..., we have the flexibility to add additional designations," said Sullivan.
Washington has repeatedly called on Assad to change course, embrace reform and allow Syrians their human and political rights, but has so far not called for Assad to go.
US Secretary of State Hillary Clinton renewed these calls on Friday, demanding that Assad immediately cease violence.
"We continue to condemn in the strongest possible terms the absolutely deplorable actions that the Syrian government is taking against its own people. The violence must end immediately," she told reporters.
Obama also renewed previously imposed sanctions on Syria, imposed by former president George W. Bush in 2005 as Washington accused Damascus of involvement in the assassination of former Lebanese prime minister Rafiq Hariri.
The sanctions were unveiled as tens of thousands of protesters poured onto the streets across Syria following a call for a "day of rage" against the Assad government after weekly Muslim prayers.
Earlier, the 47-nation UN Human Rights Council voted for a revised US-led resolution on the crackdown in Syria that asked the UN rights chief to send an investigative mission to the country.
At least 62 people died in Syria on Friday as security forces clashed with protesters defying the crackdown in the restive cities of Daraa, Homs and Latakia, a human rights group said.