This image taken from an online video purports to show ISIS threatening to kill two Japanese hostages. (The Associated Press)

The Islamic State in Iraq and Syria group threatened to kill two Japanese hostages Tuesday unless they receive $200 million US in 72 hours, directly demanding the ransom from Japan's premier during his visit to the Middle East. Prime Minister Shinzo Abe vowed to save the men, saying: "Their lives are the top priority''.