BEIRUT – An online video showed more than a dozen bloodied corpses, some of them piled atop each other and in military uniforms, dumped beside a road in northern Syria in what the government Friday called a mass killing by rebel forces.

The circumstances of the deaths were not immediately clear, with the state-run news agency saying at least 25 men were killed. In the video – which The Associated Press could not independently verify – the narrator said the victims were members of the “shabiha,” or pro-regime gunmen.

If confirmed, the video is yet another sign of the brutality of the Syrian conflict, which began in March 2011. As the fighting grinds on, Syria is descending into a civil war where gunmen prowl the streets and gruesome massacres are growing increasingly common.