BEIRUT (Reuters) - At least 13 people were killed and dozens were injured by a car bomb on Thursday which targeted a building used by a rebel group in the northern Syrian town of Azaz near the Turkish border, the Syrian Observatory for Human Rights said.

Yasser al-Yousef, from the political office of the Nour al-Din al-Zinki rebel group which controls the building, put the death toll higher at 25 and said 13 of the dead were Nour al-Din al-Zinki fighters.

It said the car bomb targeted a security office belonging to the group.

Azaz, controlled by rebel groups, has been the scene of infighting between the various insurgent groups.