A fuel tank exploded inside a clinic in the predominantly Kurdish north-eastern Syrian town of Qamishli, killing at least 25 people, many of them children.
A Syrian TV report said yesterday's explosion also wounded 30. The explosion happened as the clinic was packed with children brought to receive polio vaccinations, a Kurdish official said.
He said a gas cylinder appeared to have exploded inside the clinic, resulting in an explosion of a nearby oxygen cylinder, and the two blasts led to a third in the fuel tank, killing 25 people including 12 members of staff and children.
The British-based Syrian Observatory for Human Rights said the fire killed 25 people and some of the wounded are in critical condition.
The blast came as Isil fighters captured the town of Souran Azaz and the nearby villages of Hasya and Bel from moderate Syrian rebel groups in the northern province of Aleppo. The villages are close to the Bab al-Salamah border crossing point with Turkey.
The observatory said the fighting in the area killed 31 rebels and 22 Isil members. Isil has been fighting over territory with rebel groups in Aleppo since early last year.
In Aleppo, rebels shelled a government-held neighbourhood, killing 12 people, according to Syria's state news agency Sana, although the observatory said eight died.
The shelling came a day after Syrian army air strikes killed at least 70 people, most of them civilians, and wounded scores in attacks in Aleppo.
More than 220,000 people have been killed in Syria since the start of the uprising against Syrian president Bashar Assad in March 2011.