TOKYO >>  Prayers were offered Friday at Tokyo’s largest mosque for two Japanese hostages threatened with beheading by Islamic militants who had demanded a $200 million ransom for their release.

Militants affiliated with the Islamic State group posted an online warning that the "countdown has begun" for the extremists to kill 47-year-old Kenji Goto and 42-year-old Haruna Yukawa. The extremists gave Prime Minister Shinzo Abe 72 hours to pay the ransom, and the deadline expired Friday.

The posting, which appeared on a forum popular among Islamic State militants and sympathizers, did not show any images of the hostages, who are believed to be held somewhere in Syria.

The status of efforts to free the men was unclear. Government spokesman Yoshihide Suga was asked about the latest message and said Japan was analyzing it.

"The situation remains severe, but we are doing everything we can to win the release of the two Japanese hostages," Suga said. He said Japan is using every channel it can find, including local tribal chiefs, to try to reach the captors.

He said there has been no direct contact with the captors.

Abe met with his National Security Council on the crisis.

Japan has scrambled for a way to secure the release of Goto, a journalist, and Yukawa, an adventurer fascinated by war. Japanese diplomats had left Syria as the civil war there escalated, adding to the difficulty of contacting the militants holding the hostages.

Yasuhide Nakayama, a deputy foreign minister sent to Amman, Jordan, to coordinate efforts to save the hostages, told reporters he had no new information.

"We want to work until the very end, with all our power, to secure their release," he said.

Worshippers at the mosque in Tokyo included the hostages in their prayers.

"All Muslims in Japan, we want the Japanese hostages to be saved as soon as possible," said Sandar Basara, a worker from Turkey.

Goto’s mother made a tearful appeal for his rescue.

"Time is running out. Please, Japanese government, save my son’s life," said Junko Ishido. "My son is not an enemy of the Islamic State."

Ishido said she was astonished and angered to learn from her daughter-in-law that Goto had left for Syria less than two weeks after his child was born in October to try to rescue Yukawa.

In Japanese fashion, Ishido apologized repeatedly for "all the trouble my son has caused." She said she had not had any contact with the government.

Suga said Thursday the government had confirmed the identities of the two hostages, despite discrepancies in shadows and other details in the ransom video that suggested it might have been altered.

Japanese officials have not directly said whether they are considering paying any ransom. Japan has joined other major industrial nations in the Group of Seven in opposing ransom payments. U.S. and British officials said they advised against paying.

Two Japanese who said they have contacts with a leader in the Islamic State group offered Thursday to try to negotiate, but it was unclear if the government was receptive to the idea.

Ko Nakata, an expert on Islamic law and former professor at Kyoto’s Doshisha University, and freelance journalist Kousuke Tsuneoka are both converts to Islam. They said they have a contact in the Islamic State group and are prepared to go.

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Associated Press writers Ashraf Khalil, Kaori Hitomi and Ken Moritsugu contributed to this report.