BEIRUT -- Syrian security forces opened fire on tens of thousands of protesters across several cities Friday, killing at least 20 people, wounding hundreds and forcing residents to turn mosques into makeshift hospitals, witnesses and a human rights group said.

Ammar Qurabi, who heads Syria's National Organization for Human Rights, said most of the deaths happened in Daraa, a restive southern city that has become a flashpoint for anti-government protests.

Sixteen people were killed in Daraa, three in the Damascus suburb of Harasta, and one in the central city of Homs, he said.

The government acknowledged violence in Daraa on Friday, but said only two people died and blamed armed thugs.

One witness who helped ferry the dead and wounded to the city's hospital said he was among thousands of people at the protest and he witnessed security forces shooting live ammunition.

"My clothes are soaked with blood," he said by telephone from Daraa. Like most activists and witnesses who spoke to The Associated Press, he requested anonymity for fear of reprisals.

A nurse at the hospital said they had run out of beds; many people were being treated on the floor or in nearby mosques.

Protest organizers have called on Syrians to take to the streets every Friday for the past three weeks, demanding change in one of the most authoritarian nations in the Middle East. The protests have rattled the regime of President Bashar Assad, whose family has ruled Syria for nearly 40 years.

The witness accounts coming out of Syria could not be independently confirmed because the regime has restricted media access to the country. Human rights groups said around 115 people have been killed in the security crackdown.

Witnesses in several other cities across Syria also reported protests Friday. An eyewitness in the coastal city of Latakia said hundreds of people took part in a largely peaceful protest Friday calling for political freedoms.

"Peaceful, peaceful!" they shouted, marching past soldiers who were deployed in force in and around the religiously mixed city where clashes two weeks ago killed 12 people. He spoke on condition of anonymity for fear of reprisals.

Activists said protests also erupted in the central cities of Homs and Hama, the coastal city of Banyas, the northern city of Aleppo and outside the capital, Damascus.

A video posted by activists on Facebook showed a crowd of people in the Damascus suburb of Harasta shouting "We want Freedom!" and "The Syrian people will not be humiliated." The footage could not be independently confirmed.

The state-run News agency said a police officer and an ambulance driver were killed Friday in Daraa. The report blamed "armed men" for the violence. The government has blamed much of the unrest in recent weeks on armed thugs.

It was not clear if SANA and the eyewitness were counting the same people.

The Interior Ministry called on residents of Daraa not to provide shelter for the armed groups that opened fire on civilians and police and to provide authorities with any information they have about them. (AP)