Syrian rebels took control of army checkpoints guarding the entrances to the critical Euphrates River dam in the northeastern province of Raqa activists said.
"There is little resistance in the area and it looks like the battalions will push through to the control rooms of the dam in the coming hours," the Syrian Observatory for Human Rights reported.
Rebels from the jihadist Al-Nusra Front and the Awayis al-Qurani and Ahrar al-Tabqa battalions took control of three districts in the town of Tabqa on the Euphrates and captured a number of security force members, it said.
"If the rebels are able to control the Euphrates dam, it will be a painful blow to the regime," the activists said.
Activists posted on YouTube a video showing, small groups of men dressed in black uniforms can be seen running across a main street of Taqba with their hands in the air amid barrages of gunfire and the sound of echoing blasts.
The video, apparently filmed in Tabqa, could not immediately be verified.