According to the United Nations, over 2,50,000 people have been killed in the civil unrest in Syria. (Reuters file photo)
Opposition activists say an explosion at offices used by an ultraconservative militant group in northern Syria killed at least seven people.
The Local Coordination Committees said a car bomb exploded near a building used by the Ahrar al-Sham group in the city of Aleppo on Monday, killing seven people and wounding others.
The Britain-based Syrian Observatory for Human Rights put the death toll at 23.
The Opposition group, which relies on local activists, said the attack was carried out by a suicide bomber driving a tanker truck. The Observatory says the dead include four local Ahrar al-Sham commanders.
The Turkey and Saudi-backed Ahrar al-Sham has been fighting against the Islamic State group for two years.
No one claimed responsibility for the attack, which damaged several buildings.