The deadline set by Islamist militants threatening to kill two Japanese men unless they were given $200 million passed Friday, after one captive's mother made a desperate plea to save her son's life.
Japan had heard nothing from the extremists holding Kenji Goto, a freelance journalist, or Haruna Yukawa, the self-employed contractor who he had gone to rescue, the chief government spokesman said.
"There has been no message" from the Islamic State group since the 72-hour deadline expired at 2:50 pm (0550 GMT) Friday, Yoshihide Suga told reporters.
"The situation remains very severe, but the government is making its utmost efforts, asking for cooperation from many countries and heads of ethnic groups."
Reporters waiting for any announcement on the two men's fate said Prime Minister Shinzo Abe looked tired and drawn as he rushed from one commitment to the next.
Hours earlier, Junko Ishido launched an emotional appeal for mercy for Goto, her son.
"I say to you people of the Islamic State, Kenji is not your enemy. Please release him," she said.
"Kenji was always saying 'I hope to save lives of children on battlefields'. He was reporting war from a neutral position."
The high drama in Tokyo comes three days after the sudden release by the Islamic State group of a video in which Goto and Yukawa, apparently kneeling in the desert, are threatened with execution by a British-accented man.
"You now have 72 hours to pressure your government into making a wise decision by paying the $200 million to save the lives of your citizens," he said.
- Earmarked funds -
The Islamists linked the ransom to the amount of cash Abe said he would be earmarking to help countries dealing with the influx of refugees fleeing fighting between IS and regular forces.
Asked by a journalist if she thinks Tokyo should pay the ransom, as it has in previous hostage situations, Ishido said: "Yes, I very much hope so."
"Japan has maintained a friendly relationship with Islamic nations.
"The time remaining is scarce. I beg you Japanese government officials, please save Kenji's life."
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Tokyo is under pressure from Britain and the United States to stand firm on the ransom, as both countries have a policy of never paying ransoms.
Ishido, who was identified as Goto's birth mother, said she had learned Thursday that his wife had given birth two weeks ago when the two spoke on the telephone for the first time.
"Kenji left for the IS with a gentle heart hoping to save a life of his Japanese colleague," she said, referring to reports that Goto had been on a mercy mission to rescue Yukawa.
"He didn't care about his safety because he believed he and people of IS would be able to understand each other, as members of the global community."
She also said she has had no contact at all with the Japanese government since video of Goto and Yukawa emerged on Tuesday.
A spokesman told AFP the administration was in close contact with family of the missing men, but refused to elaborate.
- Statement -
NHK reported early Friday it had a text and audio exchange with a "public relations" official from the Islamic State group.
The representative was quoted as saying: "Japanese are infidels fighting against Islamic State."
Asked about the Japanese efforts to negotiate the release of the two hostages, he said, "We cannot answer that because it isn't a good question."
"A statement will come out sometime later," he said, without giving further details.
The Japanese media has rallied around Goto, a respected and experienced war reporter whose work has appeared on domestic television channels.
In video footage he filmed around the time he entered Syria, he holds identification papers and his Japanese passport and explains that he is aware of the risks.
"Whatever happens, I am the one who is responsible," he says. "I am asking you, Japanese people, do not place responsibility on the people of Syria. Please. I am sure I will come back alive though."
The IS group has previously killed three Americans and two Britons after parading them on camera, but this is the first time Japanese citizens have been threatened, and the first time a ransom demand has been made in this way.