Protesters have marched through the Syrian city of Deraa, chanting anti-government slogans at the funeral of activists killed on Wednesday, witnesses say.
Some accounts claimed 20,000 people were out on the streets, but the number was impossible to verify.At least 15 people are known to have died in clashes between security forces and protesters on Wednesday.
Security forces have ringed the city in a bid to quell unrest.
Activists have been using social-networking websites to call for nationwide protests after Friday prayers.
Challenge
There are reports of mass arrests as the government of President Bashar al-Assad seeks to calm the situation.Analysts say the unrest is the biggest challenge Mr Assad has faced since he took over from his late father 2000.
Reuters news agency quoted witnesses as saying mourners at Thursday's funeral chanted: "God, Syria, freedom. The blood of martyrs is not spilt in waste."
An activist in Deraa told AFP news agency the mourners had begun their procession from the Omari mosque - the focal point of protests, and scene of some of the worst violence.
There were no reports of renewed violence.
Wednesday's clashes erupted in the early hours when security forces tried to storm the mosque.
The authorities said in a statement they were targeting armed gangs that "stocked weapons and ammunition in the mosque and kidnapped children and used them as human shields".
Hundreds of people had gathered at the mosque to try to prevent security forces from getting in.
Reports say several people were killed in subsequent clashes, including a medical worker who was treating an injured protester.
'Bullet holes'
The worst violence was said to have happened in the early evening, when crowds of protesters from surrounding villages tried to get into the city to demonstrate.Witnesses and activists told reporters that security forces opened fire indiscriminately.
It was not immediately clear how many people had died.
On Thursday, a hospital official in Deraa told Reuters they had received 25 bodies, adding: "They all had bullet holes."
Rights activists supplied the CA with a list of 45 people they said had been killed in the unrest.
The CA's Lina Sinjab in Damascus says the number of dead is difficult to verify because some of the protesters could have been taken to hospitals in other towns and cities.
Syria has been ruled under emergency laws since 1963, and the government tolerates no dissent.
Unrest broke out last Friday in Deraa when locals campaigned against the detention of 15 children, held apparently for daubing anti-government slogans on walls.
The authorities opened fire on the demonstrators, sparking more radical protests calling for political reform on the following days.
If confirmed, Wednesday's violence would be the worst since the unrest began.
The government has consistently denied the numbers of casualties claimed by witnesses and activists.
The authorities have claimed to be targeting "infiltrators" and "troublemakers" trying to spread fear among the population.
