TOKYO (Yomiuri Shimbun/Asia News Network) - A group who claimed to have taken Kenji Goto hostage sent about 10 e-mails to his wife from late November to early January, demanding ransom, according to government sources.

The group, which is believed to be the Islamic State in Iraq and Syria (ISIS), demanded 2 billion yen (S$22.8 million) in ransom in the e-mails. However, in the video released online by ISIS on Tuesday, the captor demanded a far higher sum of $200 million (S$267 million) in exchange for the lives of Goto and another Japanese hostage, Haruna Yukawa, by Friday.

The Japanese government therefore believes there was a change within the group regarding the negotiations over the Japanese hostages. The government is continuing to gather information.

The deadline, believed to be 2.50pm Friday Japan time (1.50pm Singapore time), has passed quietly, without further signals from the captors.

A member of the group first e-mailed Goto's wife in late November, according to the sources. She noticed the existence of the e-mail in December and opened it to read the English message, which claimed the group had detained Goto. The wife then contacted the government.

Later, the wife replied to the sender, and by early January, the group had sent her about 10 messages, demanding about 15 million euros (S$22.51 million), in ransom.

The e-mail messages contained some information that only Goto knows, and the sender's e-mail address was the same as that used in sending messages in other cases in which foreigners were taken hostage by ISIS militants.

In light of these facts, the government concluded it was highly likely that Goto was taken hostage.