Fighting inside Syria
Meanwhile, Syrian rebels claimed to have captured Syria's largest man-made dam on Monday.
"The Free Army took control of the city of Tabqa and the Euphrates (Tabqa) Dam," the opposition Media Center in Tabqa announced in an online posting.
"If clashes will happen, this will cause big damage and the whole area will drown and many places will lose electricity."
CNN could not independently confirm claims that the dam had been captured. The Syrian government did not respond to opposition claims that its forces had lost control of the dam.
The Tabqa Dam was completed in the 1970s with the help of thousands of Syrian and Soviet workers. It houses a hydroelectric power station.
The dam sits at the end Assad Lake, a man-made reservoir on the Euphrates River named after the father and son who have ruled Syria for the past four decades.
Opposition groups distributed videos of Syrian rebels seizing caches of weapons and ammunition from positions once held by Syrian security forces.
They also showed video of what appeared to be the dam itself, towering over the surrounding countryside.