The Obama administration slapped sanctions on three Syrian officials and Syria’s intelligence service on Friday in what was described as a warning shot against President Bashar al-
Assad’s government after weeks of steadily worsening violence against protesters.

The measures targeting key members of Assad’s security apparatus came amid reports of dozens more deaths across the country as Syrians rallied in several cities — including, for the first time, in large numbers in Damascus, the capital — for a national “Day of Rage” denouncing government brutality.

Tens of thousands of Syrians poured out of mosques and into the streets after Friday prayers for what appeared to be the biggest demonstrations yet in the country. The large turnout, after days of deadly clashes, suggests that the will of the protesters remains unbroken despite the government’s stepped-up efforts to crush the uprising.

Human rights groups said that at least 48 people were killed nationwide when troops opened fire on demonstrators on Friday. Fifteen of them were killed outside the southern town of Daraa, the epicenter of the protests and a rallying point for the uprising after civilians there were besieged by army tanks on Monday.

The Obama administration, facing pressure at home and abroad to act against the Assad regime, announced that it was freezing the assets of Syria’s intelligence service and its director, Ali Mamluk, as well as those of Maher al-Assad, the president’s brother and a brigade commander in Syria’s 4th Armored Division. White House officials said the army unit and the intelligence agency played leading roles in the violent attacks that have killed hundreds of people since March 16.

The administration also announced sanctions on Atif Najib, the president’s cousin and a political operative in Daraa province, and on Iran’s Quds Force, a paramilitary division of that country’s Revolutionary Guard Corps. A Treasury Department statement announcing the sanctions accused the Iranian group of providing material support to the Syrian intelligence service in the crackdown.

U.S. officials made clear that the sanctions were intended to pressure Assad to halt the violence. The presidential order authorizing the economic penalties also permits the administration to add the names of any Syrian government officials who participated in the attacks on protesters or were “complicit” in them.

“This sharpens the choice for Syrian leaders who are involved in the decisions,” Jake Sullivan, the State Department’s director of policy planning, told reporters shortly after the sanctions were announced.

Another administration official familiar with internal discussions about Syria policy added: “If this continues, Assad could be next.”

Few diplomatic options

The White House has been frustrated by a lack of diplomatic options in dealing with Syria, a country that is barred from most trade with the United States and is labeled a terrorist-sponsoring nation by the State Department. Washington continues to maintain formal diplomatic ties with Damascus, and the administration has not called on Assad to step down, as it did in the case of Libyan leader Moammar Gaddafi and now-deposed Egyptian President Hosni Mubarak.

Several key congressional leaders this week pressed the administration to break publicly with Assad, saying the Syrian leader has lost legitimacy. On Friday, the U.N. Human Rights Council, meeting in Geneva, added to the pressure with a resolution condemning the killing of protesters and appointing a delegation to travel to Damascus to investigate the crackdown.

Senate Foreign Relations Committee Chairman John F. Kerry (D-Mass.), who has met repeatedly with Assad and publicly encouraged the Syrian leader’s past efforts at political reform, applauded the imposition of sanctions by the White House.

“Decisions to kill unarmed civilians have consequences,” Kerry said.

The protests in Syria on Friday reportedly occurred in more than a dozen cities and included a large gathering in the central Damascus neighborhood of Midan, adjoining the historic old city, where demonstrators marched down a main street chanting, “The people want to topple the regime.” They were dispersed by troops firing live ammunition and tear gas.

Until Friday, Damascus had remained largely immune from the surge of unrest that has engulfed Syria for weeks, posing the biggest challenge yet to 40 years of Assad family rule. There were also reports of protests in dozens of other locations that previously had not experienced any unrest, said Wissam Tarif of the human rights group Insaf. He said he counted demonstrations in 104 towns and villages, compared with 43 a week earlier.

“The whole country was on the streets,” said Razan Zeitouneh, a human rights lawyer in Damascus. “This shows the Syrian people are not afraid of anything anymore.”

In the town of Deir al-Zour, several thousand people chanted “not scared, not scared,” in a challenge to the regime’s use of military force to suppress dissent, according to a video posted on YouTube. “We are going bravely to heaven in our millions,” the crowds roared.

‘Regime is in big trouble’

Although the opposition movement in Syria has yet to attract the kind of huge crowds that toppled the leaders of Egypt and Tunisia, the army’s willingness to use force has seemingly backfired, said Salman Shaikh, director of the Brookings Doha Center in Qatar’s capital.

“The regime is in big trouble and at a critical stage of survival,” he said. “We’re consistently seeing new demonstrations, and though some of them are small in scale, they are taking place across the length and breadth of the country.”

The death toll appeared to be lower than it was the previous Friday, when soldiers killed more than 100 protesters. But human rights groups said casualties were expected to rise as reports of shootings emerged from remote areas and as protests and killings continued into the night.

Although troops clearly used force to disperse protesters in some areas, demonstrations proceeded unhindered in other places, suggesting that local authorities and army units may not be united behind the regime’s strategy of using overwhelming force. Dozens of low-ranking politicians in several areas resigned last week to protest the brutality of the crackdown, and there have been persistent reports of defections from the army in the besieged town of Daraa.

Syrian state television reported that four soldiers had been killed in Daraa, though the circumstances were unclear. The government has portrayed the situation as a rebellion by armed Islamist extremists.

Sly reported from Beirut. Staff writers Mary Beth Sheridan and Scott Wilson contributed to this report.