In its first detailed statement on the incident, the ICRC said on Sunday night Louisa Akavi, Alaa Rajab and Nabil Bakdounes were seized in October 2013 while travelling to Idlib province in north-western Syria, the BBC reported.
Akavi, a citizen of New Zealand, is a 62-year-old nurse who has carried out 17 field missions, while Rajab and Bakdounes, both Syrian nationals, worked as drivers who delivered humanitarian assistance in the country.
Akavi was held by the Islamic State group and there is evidence she was alive in late 2018, according to the ICRC. The fate of Rajab and Bakdounes is not known.
"The past five and a half years have been an extremely difficult time for the families of our three abducted colleagues. Louisa is a true and compassionate humanitarian. Alaa and Nabil were committed colleagues and an integral part of our aid deliveries," said Dominik Stillhart, ICRC's director of operations.
"We call on anyone with information to please come forward. If our colleagues are still being held, we call for their immediate and unconditional release."
Meanwhile, the New Zealand government on Monday said that a special forces team has been trying to locate Akavi.
"This has involved members of the NZDF (New Zealand Defence Force) drawn from the Special Operations Force, and personnel have visited Syria from time to time as required," said Deputy Prime Minister Winston Peters told the media.
"This non-combat team was specifically focused on locating Louisa and identifying opportunities to recover her."
In 1999 she was awarded the Florence Nightingale Medal for services to nursing.
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