Syrian rebels are battling both fighters of the Islamic State (IS) militant group and, separately, government soldiers as they try to hold on to strongholds in the north of the country near Aleppo.
Syrian opposition groups said on May 28 that IS militants clashed with rebels holding the town of Marea as the extremist group builds on its most significant advance near the Turkish border in two years.
Meanwhile,Syrian Army warplanes and helicopters hit other opposition-held towns in Aleppo province, putting a further strain on rebels fighting President Bashar al-Assad's forces.
Media reports say that more than 160,000 civilians have been trapped by the fighting.
The IS territorial gains north of the city of Aleppo come despite the group having suffered a string of recent losses in Syria and Iraq.
Syrian Rebels Fight IS, Government Forces Near Aleppo