The place where the Syrian uprising began two years ago, the Omari mosque in the city of Daraa, crumbled Saturday amid fighting between rebels and government forces.
The minaret is shown toppling into a cloud of dust in a video posted on YouTube. The cameraman says government forces are the ones who brought it down, but his claim cannot be independently verified by CNN.
Daraa was one of several places where rebels and government forces clashed on Saturday, according to activist groups.
Throughout the past two years, the Omari mosque has been a gathering place for protesters, the center of anti-government demonstrations in the city. At the start of the uprising, it was briefly used as a civilian hospital for wounded protesters.
The mosque was the first place protesters gathered in March 2011 to protest the arrest and alleged torture of teenagers who sprayed anti-Assad graffiti, sparking the waves of weekly peaceful demonstrations that eventually spread across the country.
The Local Coordination Committees of Syria, an opposition group, said there was shelling using surface-to-surface missiles and phosphorus bombs in Daraa and other parts of the country.
By the end of Saturday, 115 people were killed in Syria, including 12 in Daraa, the Local Coordination Committees said.
Syrian activists tell CNN the government is using an increasing number of phosphorus bombs, incendiary weapons that can cause serious chemical burns. They are controversial but not banned by any treaty.
"Phosphorus burns on the skin are deep and painful," according to GlobalSecurity.org, a military research website. It says the burns are usually multiple and deep, down to the bone, and the particles will continue to burn unless deprived of oxygen.
Activists reported an incident of phosphorus bombs in Merayiya, in Deir Ezzor province, on Friday. The Local Coordination Committees reported helicopters dropped phosphorus bombs over the town of Khirbet Ghazaleh in Daraa province Saturday.
Video posted to YouTube on Friday is purported to show Merayiya. Thin streams of white smoke fall out of the clear sky onto pastoral farmland, where small fires then dot the landscape and create smoke that blankets the area.
Another video on YouTube, posted Saturday, apparently of Khirbet Ghazaleh, shows a small fire burning in the bricks and rubble of a house, emanating heavy white smoke.
CNN cannot verify the authenticity of the videos.
Phosphorus bombs often are used for smoke screens and become luminous in the dark, GlobalSecurity.org says.
Human Rights Watch says incendiary weapons such as phosphorus bombs "produce terrible scarring and disfigurement. The victims who survive endure painful treatments, suffer from psychological trauma and, in some cases, are ostracized by society."
Fighting raged Saturday in the Syrian capital of Damascus, a spokesman for the Abu Qtada Military Council told CNN. There were clashes at the gates of the city, in the Yarmouk refugee camp, and in the Damascus suburbs, where he reported artillery shelling by government troops.
The Italian Foreign Ministry reported Saturday that four Italian journalists who were held hostage in Syria for more than a week were released.
The Italian news agency ANSA reported the group was abducted in northern Syria on April 5. It said they were taken to Turkey after their release.