Assad has tried to face off the protests, which spread from the southern city of Deraa, by a mixture of force, vague promises of reform and reaching out to minority Kurds and conservative Sunni Muslims.
Emergency law in force since the Baath Party took power nearly 50 years ago bans any public gatherings of greater than five people. Demonstrations after midday Friday prayers have tended to be the strongest in numbers.
They have also been among the most bloody, with witnesses saying security forces have fired on protesters. Authorities blame "armed groups" and "infiltrators" for the violence.
Rights groups say at least 200 people have died in protests that have posed the greatest challenge to Assad's 11-year rule.
The United States said it believes there is evidence Iran, which shares with Syria a strong anti-Israeli alliance, is assisting Damascus in quelling the protests.
Syria denied the U.S. allegations. "There is no truth to the announcement by the U.S. State Department about the presence of evidence of Iranian help to Syria in quelling the protests," state television quoted a Foreign Ministry official as saying.
RESTIVE CITY OF BANIAS
A rights group reported that authorities had freed hundreds of people in the restive coastal city of Banias, which security forces had sealed off and surrounded with tanks after a demonstration last week.
The move was part of a deal struck in Damascus between a Baath Party official and imams and prominent figures from Banias, intended to help calm the city ahead of Friday prayers.
Syria said snipers shot dead a soldier in Banias Thursday and wounded another.
The Syrian Observatory for Human Rights, which reported that hundreds of Banias detainees had been freed Thursday under the deal, said it had documented several cases of torture.
"Some swore they were interrogated about things they never heard of in their lives," it said in a statement, calling for an independent legal investigation.
The group said authorities had pledged to improve living conditions in Banias and withdraw secret police, replacing them with troops who would safeguard residents.
Irregular loyalists to Assad, known as 'al-shabbiha', killed four people in Banias Sunday, a rights campaigner said.
The United States, France, Britain and other nations have urged Assad to refrain from violence in dealing with protests.
Some of the tension has sectarian overtones in a mostly Sunni Muslim nation ruled by minority Alawites, adherents to an offshoot of Shi'ite Islam.
The unrest in Syria started last month after police detained more than a dozen children in the southern city of Deraa for graffiti inspired by democracy protests across the Arab world.
Such demonstrations would have been unthinkable a couple of months ago in this tightly controlled country.
A delegation from Deraa, which has seen the bloodiest clashes since unrest first broke out on March 18, met Assad in Damascus Thursday to discuss the crisis. The delegation included state employees and tribal figures, but other prominent figures in the city refused to go, a source in Deraa said.
Protests have not reached the critical mass seen in uprisings in Tunisia and Egypt. A heavy secret police presence, preachers on the state payroll giving pro-Assad sermons and a Sunni merchant class staying on the sidelines have helped prevent major protests reaching central Damascus and Aleppo.
But religiously conservative Sunni areas along Syria's coastline have defied a campaign of arrests and security sweeps designed to stop the unrest from taking hold of the country.
Opposition figures said any genuine reforms in Syria to allow people more freedom would require an effective executive branch and independent judiciary to replace a powerless government structure dominated by the Baath Party.
(Additional reporting by Mariam Karouny and Yara Bayoumy in Beirut and Suleiman al-Khalidi in Amman; Editing by Janet Lawrence)