Here is look at foreign hostages believed held by the Islamic State group and some of those who have been released, reportedly in exchange for ransom payments:
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JOHN CANTLIE (pictured): British photojournalist who appeared in several Islamic State propaganda videos delivering statements, purportedly from the Syrian border town of Kobani and the Iraqi city of Mosul, likely under duress. He was kidnapped with American journalist James Foley in November 2012. An Islamic State group militant beheaded Foley last August.
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FATHER PAOLO DALL'OGLIO: The Italian Jesuit priest went missing in July 2013 after traveling to meet Islamic militants in the Syrian city of Raqqa.
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SAMIR KASSAB: A Lebanese cameraman for satellite channel Sky News Arabia. He was kidnapped Oct. 15 while working near Aleppo, Syria's commercial capital and the scene of heavy fighting since rebels seized part of the city in 2012.
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ISHAK MOKHTAR: A Mauritanian reporter for Sky News Arabia. He was kidnapped Oct. 15 while working near Aleppo.
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UNIDENTIFIED AMERICAN WOMAN: She was captured last year in Syria while working for aid groups. U.S. officials have asked that the woman not be identified out of fears for her safety.
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THREE WORKERS FOR THE INTERNATIONAL RED CROSS: The three were taken near Saraqeb, in Syria's Idlib province, in October 2013. The organization has declined to provide information on their identities nor who has them, citing fears for their safety.
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SEVEN LEBANESE SOLDIERS: Abducted in August in the Lebanese border town of Arsal during a cross-border militant raid from Syria.
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GRETA RAMELLI and VANESSA MARZULLO: The Italian aid workers, aged 20 and 21, returned home in January after being held hostage in Syria for more than five months.
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NICOLAS HAMMARSTROM and MAGNUS FALKEHED: Swedish freelance journalists released in January after about 90 days in captivity. Swedish officials declined to say who seized them or how they were set free.
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EDOUARD ELIAS, DIDIER FRANCOIS, NICOLAS HENIN and PIERRE TORRES: French journalists released in April after being held hostage for 10 months.
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JAVIER ESPINOSA, RICARDO GARCIA VILANOVA and MARC MARGINEDAS: Spanish journalists released in March after being held hostage for months.
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