Damascus: Jihadists battling rebels in northern Syria have sought to recover turf lost during nearly a week of fighting between them that has killed hundreds in the latest twist in the civil war.
Thursday's fighting came a day after the Islamic State of Iraq and the Levant (ISIL) was expelled from the devastated former commercial capital of Aleppo by rebels fighting to topple President Bashar al-Assad.
Meanwhile, a massive car bomb blast in Kafat in the central province of Hama killed at least 18 people, including women and children, the Syrian Observatory for Human Rights said.
And at least 45 rebels were killed when they tried to break an army siege in the central city of Homs. Observatory director Rami Abdel Rahman said the rebels had launched an attack late on Wednesday near the Khaldiya neighbourhood, controlled by the army, when they were ambushed.
The violence comes nearly a week after rebels launched an all-out attack on ISIL, and almost three years into a war that erupted after Dr Assad cracked down brutally on a peaceful pro-democracy movement.
Jihadists were initially welcomed by Syria's rebels, but ISIL became hated because of its systematic abuses and its bid to dominate areas lost to the regime.
In a counterattack, ISIL launched car bomb assaults late on Wednesday against rival rebel checkpoints, the Observatory said.
"At least nine people were killed in a car bomb attack by ISIL on a rebel checkpoint ... in Al-Bab town" in Aleppo province, Mr Abdel Rahman said.
There were similar attacks in Hreitan and Jarabulus in Aleppo and in Mayadeen in the eastern province of Deir Ezzor.
The attacks came after rebels overran ISIL's Aleppo headquarters on Wednesday, as claims emerged that the group had massacred prisoners there.
In Raqa, the only provincial capital lost by the regime, fighting raged near the state building, which ISIL has used as its headquarters for several months. While rebels in Raqa appeared to be advancing, ISIL was fighting back in the countryside, especially in the border town of Tal Abyad, from which they were expelled earlier this week.
ISIL is believed to be holding hundreds of activists, rival rebels and foreigners, including journalists, at bases in Raqa province. Activists say Raqa has become "a city of ghosts", with bodies in the streets and people afraid to leave their houses because of the violence.
The fighting has not stopped the main war with the regime. In Aleppo, warplanes carried out a new air strike on the rebel-held district of Sheikh Maqsud. A brutal aerial offensive by the regime against Aleppo that started on December 15 has killed hundreds, mostly civilians.