Syrian rebels pressed an offensive in the Damascus and Aleppo provinces, in an escalation that has killed 194 fighters on both sides in the past three days, a monitoring group said Monday.
Rebels in Eastern Ghouta, east of Damascus, are trying to break the army siege on opposition areas there, taking over several small villages and checkpoints, said the Syrian Observatory for Human Rights.
"In the past three days, the rebels have taken over small villages and checkpoints east of Damascus and southeast of Aleppo, after launching counter-offensives on those fronts," said Observatory director Rami Abdel Rahman.
Since Friday, 194 fighters on both sides have been killed, as well as seven anti-regime media activists.
On the rebel side 115 rebels were killed, including 50 jihadists from the Islamic State of Iraq and the Levant and Al-Nusra Front, said the Observatory.
The dead on the loyalist side included five members of Lebanon's Shiite Hezbollah and 20 fighters from the Iraqi Abdul Fadl al-Abbas militia, as well as 46 government troops and eight members of a pro-regime militia.
Southeast of Aleppo, rebels also battled to turn back recent advances by the army, which has gained the upper hand against the rebels at key battle fronts in recent weeks.
"Now the army is no longer advancing there," Abdel Rahman said.
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Opposition activists have described the counter-offensive in Damascus as a bid to break a siege that has prevented weapons and humanitarian supplies from entering the Eastern Ghouta area.
The main opposition National Coalition has linked the rebel advance to Friday's merger of Syria's biggest Islamist rebel groups, which did not include jihadists.
According to the Observatory, the army used intense firepower to fight back, launching air strikes around Damascus.
On the ground, Lebanon's "Hezbollah is leading the fighting. Hundreds of its fighters have been deployed to Eastern Ghouta," said Abdel Rahman.
A security source in Damascus meanwhile told AFP that "the rebels have taken seven small villages, while the army has taken back three of them."
The rebels "are trying to take over Otaybeh, but they will not succeed."
Otaybeh is strategically located east of Damascus, and until April this year had been used by rebels as a point of entry into Damascus from one of their main supply routes from the Jordan border.
Pro-regime Al-Watan newspaper meanwhile said the army was deploying troops in the town of Deir Attiyeh, north of Damascus, "in preparation to take it back" from rebel hands.
Located in the strategic area of Qalamoun along Lebanon's border, Deir Attiyeh is home to a sizeable Christian community and was taken over last week by rebels, among them jihadists.
In two and a half years, Syria's war has killed at least 120,000 people, and forced millions more to flee their homes.