SYRIAN rebels say they have overrun army positions in the north and south of the country this week, including an offensive in which a rights monitoring group said 51 soldiers were executed.

Insurgents have focused on taking isolated army outposts, mostly in rural areas while forces loyal to President Bashar al-Assad have made gains around the capital Damascus and the central city of Homs.

One video, posted on YouTube on Wednesday by a rebel group calling itself the Supporters of the Islamic Caliphate, shows around 30 men's bodies piled up against a wall. "Tens of Assad's (militia) killed," says a man off camera. He said the footage was filmed in the town of Khan al-Assal, which was taken by rebels last week.

The Syrian Observatory for Human Rights, an anti-Assad monitoring group, cited activists in Khan al-Assal who said more than 150 soldiers were killed on Monday and Tuesday in and around the town, including 51 who were executed.

Another video, posted by a rebel group in the village of Hara in the southern province of Deraa, shows several dead soldiers in a room.

"These are Assad's dogs," says a voice off screen.

Assad's forces have been on the offensive since last month when the army, backed by militants from Lebanese group Hezbollah, recaptured a border town near Lebanon straddling supply lines between Damascus and the coast.