Syrian forces killed at least 19 people in raids near the Lebanon border and in the country's Sunni tribal heartland, activists said, pursuing a military campaign to crush street protests against President Bashar al-Assad.
Assad's forces have intensified assaults on towns and cities across the country since the start of the Muslim fasting month of Ramadan to subdue mounting dissent against the ruling family, despite threats of new U.S. sanctions and calls from Turkey, Syria's powerful northern neighbour, and Arab nations, to halt the attacks.
"Assad remains convinced that the military solution is working, ignoring the fact that as soon as he contains demonstrations in one town they erupt in another," a Western diplomat in the Syrian capital said.
"At one point he may not have enough loyalist troops capable of exerting control over simultaneous centres of protests," he added. Assad belongs to Shia Islam's minority Alawite sect.
Activists and rights campaigners said 11 civilians, including a woman and a child, were killed on Thursday when troops and tanks swept into Qusair, 135 km (85 miles) north of Damascus, after overnight protests calling for Assad's removal.
In nearby Homs, activists said on Friday that five people, including a nine-year-old boy, were killed in an overnight raid on the Byada residential district after protests in the city.
Nightly Ramadan prayers, or 'tarawih', which follow the breaking of the fast, have given more Syrians a focus for daily protest marches against 41 years of Assad family rule over the country of 20 million, activists said.
Syrian authorities have expelled most independent journalists since the five-month-old uprising began, making it difficult to verify reports from both sides.
In the east, troops and Military Intelligence personnel, backed by armoured vehicles, stepped up their assault on Deir al-Zor, capital of an oil-producing province bordering Iraq's Sunni heartland.
Four civilians were killed in house-to-house raids in Deir al-Zor on Thursday and several shops belonging to families of prominent dissidents in the city were burned down, the Syrian Observatory for Human Rights said.
One person was killed in the coastal city of Latakia.
About 14 tanks and armoured vehicles swept into Saraqeb, a town on Syria's main north-south highway that has seen daily demonstrations, and security forces arrested 100 people, residents said by telephone.
The tanks later withdrew and residents staged a night-time rally in the town's streets, but security forces fired at the demonstrators, injuring four, the Syrian Observatory said.
U.S. Secretary of State Hillary Clinton said sanctions against Syria's oil and gas industry were needed to put pressure on Assad. She called on Europe and China, main foreign players in Syria's energy sector along with Russia, to do more in imposing sanctions on Syria.
Clinton, in a CBS interview, also said an organised, united opposition was needed in Syria.
Syria's oil industry, with which the ruling family has close links, generates most of the state's hard currency from crude output of 380,000 barrels per day.
Asked why the United States had not called on Assad to step down, Clinton said the United States had been "very clear" in its statements about Assad's loss of legitimacy, and wanted other nations to add their voices.
On Wednesday Washington imposed sanctions on Syria's largest bank and on biggest mobile telephone company, controlled by Assad's cousin Rami Makhlouf, and on Thursday U.S. ambassador to Damascus Robert Ford said more sanctions would follow if the Syrian authorities did not stop their use of violence.
Regional powers Turkey, Saudi Arabia and Egypt have all put pressure on Assad to stop the violence. U.S. President Barack Obama and Turkish Prime Minister Tayyip Erdogan spoke on Thursday and agreed Syrians' demands for a transition to democracy must be met, the White House said.
Diplomats in New York quoted United Nations deputy political affairs chief Oscar Fernandez-Taranco as saying on Wednesday that nearly 2,000 Syrian civilians had been killed since March -- 188 since July 31 and 87 on Aug. 8 alone.
Syria says 500 soldiers and police have died in the bloodshed, which it blames on armed gangs and terrorists.
HAMA STREETS EMPTY, SCARRED
Syrian authorities said their tanks had pulled out of Hama, where troops crushed large pro-democracy protests in an attack that residents said killed scores of civilians, reviving memories of a massacre by the military three decades ago.
Troops sent in by Assad's father, Hafez al-Assad, overran the city in 1982 and crushed Islamist insurgents, killing many thousands of people.
Hama's main streets were empty on Thursday, windows shuttered and most shops closed after the week-long military campaign to crush dissent in a city that had become a symbol of defiance.
During a trip organised for Turkish journalists, no tanks could be seen but armed, uniformed men stood on rooftops, soldiers manned a series of checkpoints into the city, and the governor's building in the central square was flanked by two military vehicles with mounted machineguns.
The Syrian human rights group Sawasiah said at least 30 people were arrested in dawn raids in the northern countryside near Aleppo, and other arrests were made in the northern Idlib province, Damascus suburbs and the southern Hauran Plain.
The Syrian Observatory for Human Rights said rights campaigner Abdelkarim Rihawi was arrested at a cafe in Damascus.
Another activist group, the Local Coordinating Committees, said nine detainees had died from torture in detention over the last 10 days in Damascus, Homs, Deraa and Damascus suburbs.