A list of foreign hostages believed held by the Islamic State group and some of those who have been released, reportedly in exchange for ransom money:

KENJI GOTO AND HARUNA YUKAWA: The Islamic State group threatened to kill the two Japanese hostages in a video released Tuesday unless they receive $200 million in 72 hours. In August, a Japanese citizen believed to be Yukawa, a private military company operator in his early 40s, was kidnapped in Syria after going there to train with militants. Goto is a Japanese freelance journalist who went to report on Syria's civil war last year.

MU'ATH AL-KASEASBEH: The 26-year old Jordanian pilot is the first foreign military pilot to fall into IS hands since an international coalition began its aerial campaign against the group in September. He was carrying out air strikes against the militants when his F-16 went down near the Islamic State group's de facto capital of Raqqa on Dec. 24. His captors have not made any public demands for his release.

JOHN CANTLIE: The British photojournalist has appeared in several Islamic State propaganda videos delivering statements, purportedly from Kobani and Mosul, likely under duress. Cantlie has worked for several publications including The Sunday Times, The Sun and The Sunday Telegraph, and was kidnapped with American journalist James Foley in November 2012. An IS militant beheaded Foley in August 2014.

FATHER PAOLO DALL'OGLIO: An Italian Jesuit, he went missing in July 2013 after traveling to meet Islamic militants in Syria's northeastern city of Raqqa. He has not been heard from since.

SAMIR KASSAB: A Lebanese national who worked as a cameraman for satellite channel Sky News Arabia and was kidnapped Oct. 15 while working near Aleppo.

ISHAK MOKHTAR: A Mauritanian reporter for Sky News Arabia who was kidnapped Oct. 15 while working near Aleppo.

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.

3 WORKERS FOR THE INTERNATIONAL COMMITTEE OF THE RED CROSS: They were taken near Saraqeb in Syria's Idlib province in October 2013. The organization has declined to provide information on their identities or who has them, out of fears for their safety.

AROUND SEVEN LEBANESE SOLDIERS: Abducted in August during a cross-border militant raid in the Lebanese border town of Arsal.

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IS has also released several hostages, reportedly in exchange for ransom money. There has been no official confirmation from any of the countries involved.

GRETA RAMELLI AND VANESSA MARZULLO: Two Italian aid workers, aged 20 and 21, returned home this week after being held hostage in Syria by militants for more than five months.

JAVIER ESPINOSA, RICARDO GARCIA VILANOVA AND MARC MARGINEDAS: Three Spanish journalists who were released in March after being held hostage for months.

EDOUARD ELIAS, DIDIER FRANCOIS, NICOLAS HENIN, PIERRE TORRES: They were released in April after being held hostage for 10 months.

NICOLAS HAMMARSTROM AND MAGNUS FALKEHED: Swedish freelance journalists who were released in early January after a month and a half in captivity. Swedish officials declined to say who seized them or how they were set free.