"Three ICRC colleagues and the Syrian Arab Red Crescent volunteer have been released and are safe and sound. We are waiting for further information about the other three colleagues," ICRC spokesman Ewan Watson told AFP.

Syrian opposition sources in Syria said that some extremist militants were behind the kidnapping of aid workers in the northwest of the country, shortly after four of them were freed.

"The Islamic State of Iraq and the Levant (ISIL) has freed... International Committee of the Red Cross workers they abducted yesterday on the road linking Saraqeb and Sirmin" in Idlib province, said the Syrian Observatory for Human Rights.

NJF/NJF