BEIRUT: Five staff members of the medical charity Medecins Sans Frontieres (MSF) were taken from their house in northern Syria on Thursday evening and have been out of contact since then, the aid group said in a statement on Friday.
MSF did not specify the nationality of the staff, their roles, or which group took them, but said it was "in contact with all the relevant stakeholders" and trying to re-establish contact with the staff.
The group, know for sending doctors to hard-to-reach conflict zones, said the staff were allegedly taken for questioning.
The government of President Bashar al-Assad still controls some pockets of land in northern Syria but rebels fighting for his overthrow, including hardline Islamist factions, have taken swathes of territory.
MSF is not sanctioned by Damascus to distribute aid in Syria but it does operate in rebel-held areas. The statement said its doctors work in six hospitals and four health centres in the north of Syria.
Syria's 2 1/2 year civil war started after Assad's forces cracked down on pro-democracy protests leading to an armed revolt which has left more than 100,000 dead.
A United Nations document said in November that 12 U.N. staff and 32 staff or volunteers of the Syrian Arab Red Crescent have been killed since March 2011, when the crisis started, and 21 U.N. staff remained in detention.