At least four people were killed and dozens were arrested Thursday by Syrian security forces in fresh crackdowns on military defectors and wanted anti-government protesters, according to opposition activists, dpa reported.
The deaths occurred in the central city of Homs, where the activists accused the government forces of mounting a "campaign of terror."
Reports from Syria are hard to verify, as the government has barred most foreign media and international human rights from the country.
At least 57 civilians were understood to have been arrested in the northern province of Idlib, the eastern town of Deir Al Zour, the southern province of Daraa, and the coastal cities of Latakia and Banias, the Syrian Observatory for Human Rights said.
Over 70,000 people have been arrested since the pro-democracy protests started in Syria in mid-March, added the London-based observatory. Around 15,000 of them remain under arrest, according to the observatory.
Activists based in Beirut told the German Press Agency dpa that tanks were deployed in front of the Daeel public high school, located in the southern province of Daraa.
Students in Syria have been demonstrating against the regime of al-Assad and the ruling Baath Party since Sunday, the first day of the school year.
The latest protests came one day after security forces had moved into several schools around the country and detained students participating in demonstrations. Activists have claimed that Syrian security forces use schools to interrogate and torture detained protesters.
The activists, who requested anonymity for fear of reprisal, said security troops and pro-government thugs had spread a "a climate of terror" since late Monday in Homs. "Troops were searching houses, street by street, kidnapping many young people and taking them to a stadium they had turned into a prison," they added.
Meanwhile, the Local Coordination Committees (LCC), an activist network, reported that several houses were Thursday raided in the Damascus suburb of al-Zabadani. Authorities had also blocked mobile phone signals and the Internet in parts of Damascus, added activists staying in Beirut.
The latest clampdown came as activists called for demonstrations on Friday to emphasize unity of opposition against the regime of al-Assad.
Earlier in the day, an activist based in Beirut told dpa that Syrian forces were preparing wide-scale operations in several flashpoint cities in Syria.
The activist said troops were deployed to Homs and Hama in central Syria, as well as in Daraa, adding that security forces were targeting and attacking the families of activists and sympathizers of pro-democracy protesters.
"The Syrian security forces and their dogs, the intelligence, are not sparing anyone in Syria. If they look for an activist and they cannot find him in the country, they go to his family, attack or arrest them, just to put pressure on us," he said.
The Syrian Human Rights Committee said the parents of internationally known pianist Malek Jandali were attacked in their home by pro-government militiamen. The 39-year-old German-born musician, who grew up in Homs, has often expressed support for the protesters.
The committee added that it held al-Assad's government responsible for the attack and called for an end to "barbaric and unjustified acts."
Also on Thursday, the US ambassador to Damascus, Robert Ford, warned that Syria's crackdown on peaceful protesters risked sparking sectarian strife in the country. He was quoted by broadcaster Al Arabiya as saying that despite more defections during mid-September, the Syrian army is still very cohesive.
Meanwhile, the Syrian state news agency SANA reported that five security forces were killed in an ambush by "armed, terrorist groups" against a military convoy on al-Tibah al-Jeeza highway in Daraa.
The Syrian government has repeatedly claimed to be fighting armed terrorist gangs whom it accuses of killing civilians and military personnel.
Security forces have killed some 2,700 people, including at least 100 children since the anti-government protests began in March, according to the United Nations.