Nearly 60 insurgents have been killed in fighting between secular rebels and two al-Qaeda-linked groups over control of Idlib and Aleppo, two key northern cities in Syria.
The fighting pitted opponents of Syrian President Bashar al-Assad against the al-Nusra Front and the Islamic State of Iraq and Syria, or ISIS - Rami Abdel Rahman, head of the Syrian Observatory for Human Rights, told dpa on Saturday.
Most of the victims were jihadists, said Rahman, whose Britain-based group has a network of observers and informants in Syria that has chronicled the conflict since 2011.
Damascus-based activists told local media that the anti-government rebels had given the two jihadist groups 24 hours to leave the cities.
The Syrian conflict, which has lasted for nearly three years, has resulted in several radical groups imposing strict Islamic rules in areas under their control, triggering fears that the country is turning into a hotbed of Islamist militancy.
The news of the clashes comes one day after explosions hit two gas pipelines in the region, causing massive power cuts in Damascus. Syrian Minister of Electricity Emad Khamis said on Saturday that the power supply had partially resumed in southern areas.
Oil and gas pipelines have frequently been attacked during the conflict, which began in March 2011 with anti-government protests. The government has blamed the attacks on terrorists seeking the ouster of al-Assad.