BEIRUT — Protesters throughout Syria joined in large, boisterous and peaceful rallies Friday, defying a bloody government crackdown that continued despite international calls the day before for the ouster of President Bashar Assad.

Security forces loyal to Assad shrugged off the mounting international pressure, killing at least 22 people and laying siege to several opposition strongholds. The southern province of Dara, where the uprising began following the detention and torture of a group of teenagers accused of writing graffiti, bore the brunt of the violence, with security forces allegedly killing 15 people, including two children, according to activists collecting names and accounts.

According to Local Coordinating Committees, an activist network, three soldiers were also shot dead in the province when they refused to open fire on demonstrators in the town of Inkhel.

The latest round of confrontations came a day after the United States and its chief European allies called on Assad to step aside for what they termed gross violations of human rights, and suggested how little leverage the international community has over a regime that has grown accustomed to its pariah status.

The U.S. also tightened sanctions on the regime, and European leaders were discussing new economic measures, including a possible sanction on Syrian energy companies. Tunisia, where the wave of uprisings against Arab autocrats began nine months ago, and Switzerland this week joined the list of countries recalling their ambassadors to Syria.

But Friday also showed the resolve of a protest movement that has grown geographically and found ever more creative ways to challenge Assad. “Bye, bye, Bashar!” protesters taunted in English as they held up their shoes — a grave insult to the president in a Muslim culture — in the city of Homs, according to video posted to the Internet.

On a day dubbed “the promise of victory” by activists, protesters gathered even in areas that had come under attack by security forces in recent weeks, which have coincided with the Islamic holy month of Ramadan. Security forces responded with gunfire, according to witnesses and activists, despite assurances Assad reportedly made to a United Nations envoy this week that the crackdown against protesters had ended.

Young men could be seen dodging gunfire and running down an alleyway in the Damascus suburb of Harasta in one video clip. “Go away Bashar,” a man says, amid the hail of bullets. “You stopped the military operations, you dog?”

Security forces and militias have killed more than 2,000 Syrians in a five-month campaign to crush a movement aiming to topple the Assad family’s decades-old regime, according to activists and international observers. A U.N. report published Thursday accused secret police and troops of summarily executing detainees, opening fire with machine guns and helicopters against unarmed demonstrators and torturing detainees, including children. It also alleged soldiers who refused orders to kill were themselves executed.

The violence by authorities may be referred to the International Criminal Court in The Hague as early as next week.

Neither Assad’s promises of reform nor international pressure have curbed security forces’ drive to crush a determined protest movement. In Dair Alzour, a far eastern city under siege for weeks, thousands of demonstrators in five or six districts and in outlying areas were confronted by troops and plainclothes militiamen, known as shabiha, who opened fire against them, according to an activist reached by phone.

“Before the launching of the demonstrations there were more than 2,000 shabiha, security and army members,” said the activist, who requested anonymity for safety sake. “They started going toward demonstrators and fired at them, live gunfire.”

An activist in Latakia said parts of the northwestern coastal city remained under lockdown by security forces. The activist said electricity and water had been cut in the Ramel area, which includes a Palestinian refugee camp that became the focus of violence in the city.

“Security forces are breaking into houses and shops and stealing things,” he said, asking that he not be named. “The situation is scary. There are armed militiamen on the streets in some areas in the city. Some are wearing black, some are wearing regular clothes.”

A spokesman for the United Nations agency that oversees the refugee camp said that 6,000 of the 7,500 residents displaced by the violence had been located, many of them traumatized and in need of emergency money for food and medicine.

“The refugees are too frightened to return to their homes there and are not returning,” Christopher Gunness, a spokesman for the U.N. Relief and Works Agency, said in a statement. “UNRWA has not had access — draw your own conclusions about what that means about the security situation there and the state of the camp.”

The day’s violence, the activist in Dair Alzour said, was expected given the fresh international attention to the actions of Syrian authorities.

“They responded harshly because of the pressures,” he said. “They’re playing their last card. Now with this international action, they’re ready to crush the demonstrations at any price.”

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