Syrian democracy activists say security forces have killed as many as 11 civilians amid anti-government protests by more than one million people across the country.
Five civilians were killed early on Friday in the central city of Homs, 165km north of Damascus, when tanks were deployed to halt ongoing protests, residents told the Reuters news agency.
A further six were later shot dead in protests in Homs and two other places - the Damascus suburb of Mleeha and the Idlib area in Syria's northwest, according to the Ammar Qurabi, the head of the National Organisation for Human Rights, an opposition group.
Al Jazeera has not been able to verify independently reports of the violence.
Meanwhile, two explosions were heard overnight on Friday from inside the Syrian Army War College in Homs, two residents told Reuters, saying the sound of heavy gunfire was heard and ambulances were seen heading towards the compound.
"Smoke rose from inside the premises. The injured were taken to the military hospital. It looked like an operation of some sort," said one of the residents.
On Friday, protest organisers had called for mass demonstrations to show support for Homs, the AFP news agency reported. More than 50 people have been killed theresince last Saturday, Syrian activists said.
They accuse President Bashar al-Assad of causing sectarian strife among the city's Christians, Sunni Muslims and members of his Alawite minority.
In what has become a weekly occurrence, protesters took to the streets across Syria after Friday prayers, defying an intensified military crackdown on their uprising.
"More than 1.2 million people marched. In Deir az Zor there were more than 550,000, and in Hama more than 650,000," Rami Abdel Rahman, the head of the London-based independent group, the Syrian Observatory for Human Rights (SOHR), told AFP on Saturday.
Demonstrations demanding an end to Assad's rule also broke out in the Medan district of Damascus, Latakia on the coast, and the southern city of Deraa, opposition activists said.
"Demonstrators have begun to march in various Kurdish towns" in the northeastern province of Hasaka, including Amuda, Derbassiya and Ras al-Aim, Abdel Karim Rihawi, head of the Syrian League for Human Rights, said.
Police and armed groups loyal to Assad used batons to attack thousands of pro-democracy protesters in the country's mainly Kurdish city of Qamishli on Friday, witnesses said.
Hundreds more were marching in the southern town of Suweida, and demonstrations were also taking place in Idlib, particularly in Tastanas and Kafar Nubol.
At the same time, telephone communications and electricity were cut in Daraya and Douma, just outside Damascus.
Solidarity with Homs
Government forces have killed at least 22 people since Monday in Homs, according to activists.
A Syrian military official quoted by state media on Friday said that "armed terrorist groups" in the city had killed five soldiers and wounded three officers, and warned that the armed forces were ready to respond with force.
Clashes have reportedly been taking place there between Syrian army soldiers and defectors.
Members of the Local Co-ordination Committee, an opposition rights group, in Homs told Al Jazeera that there were about 100 defectors from the Syrian army engaged in the fighting.
"Elements of the army and security forces are deployed in the districts of Qabun and Rukneddin. Barricades were set up at the entrances, limiting exits and entries," Abdel Rahman of the SOHR told the AFP news agency, referring to the Homs offensive.
"Thousands of security officers are patrolling and conducting searches of homes and making arrests."
Security forces also made a show of strength in Douma, on Damascus's outskirts, especially in the market and main mosque, conducting identity checks of people including women at roadblocks, he said.
"Security officers have terrified residents while walking ostentatiously and by showing their weapons," Abdel Rahman said.
"Many people have begun to leave in fear of arbitrary arrest" after the detention of many youths in the past few weeks."