(CNN) -- The bloodied bodies lay stuffed and tangled in the back of a pickup like garbage.

Men lifted the bodies one by one and hurled from them from a bridge into a river below as cursing filled the air.

"Brother of a whore!" they shouted as the corpses splashed and the water ran red. "Animals!" "Dogs!"

At one point, a voice asks mockingly, "This is a soldier?"

Report: Syrian army stretched amid uprising

This scene, said to have been shot in Syria, surfaced in a video on YouTube, where images of anti-government ferment and violence have emerged consistently since unrest started in the nation in mid-March.

CNN could not verify the authenticity of the video, but it illustrates the hostility of the nearly five-month-old conflict across Syria between regime forces and anti-government protesters.

It is not clear who the victims were. Were they among the 1,600 civilians or 370 security forces slain in the unrest?

The posting on the video says the bodies are anti-government forces being dumped by thugs loyal to President Bashar al-Assad.

Syrian state TV has aired the video, saying that the bodies are being dumped by anti-government protesters. A banner said the incident took place in Hama over the Orontes River.

Razan Zaitouneh, a Syrian activist, said activists doubt the incident could have happened at the Hama location because the river is dry at this time of year.

But one prominent anti-government activist, who asked not to be named because of the dangers that could arise from the release of the information, told CNN the state TV account was correct.

The bodies are those of Syrian secret police killed by Syrian fighters from Iraq who have joined the anti-government fight, said the activist, who gets information about the goings-on in Syria from an extensive network of informants.

That same activist stressed that the antagonists are not representative of the protest movement.

Violent fringe elements have appeared during the Syrian tumult. One study last month from the International Crisis Group said some anti-government elements have taken up arms.

However, that report said, "the vast majority of casualties have been peaceful protesters, and the vast majority of the violence has been perpetrated by the security services."

The activist said the emergence of this video is a double-edged sword for protesters.

On the one hand, the peaceful demonstrators need to become aware of the existence of fringe elements, he said. This would encourage more people to reject both the regime and these types of attacks and maintain the aims of peaceful protest, he said.

At the same time, he added, the incident gives credence to the Syrian government's assertion that it is targeting "armed gangs." Such violence, he said, could cause the international community to hesitate in continuing its mounting pressure against the Syrian regime.