The mother of a Japanese hostage facing beheading at the hands of Islamic State (Isis) jihadists in Syria has made an emotional appeal to his captors to set him free.

Junko Ishido pleaded with the Islamist militants, whose 72-hour deadline has just expired, to spare the life of her journalist son, Kenji Goto, 47.

"Kenji is not an enemy of the Islamic State. Please free him," she said tearfully, speaking before the Foreign Correspondents' Club of Japan in Tokyo, The Asahi Shimbun reported.

Goto, an experienced freelance war correspondent appeared kneeling in the desert in an orange jumpsuit alongside another Japanese hostage, Haruna Yukawa, 45, in a video released by Isis this week.

Between them in the footage is a knife-wielding, black-clad militant who threatens to behead the pair if the Japanese government doesn't pay a $200m (£132m, €173m) ransom by today.

The blackmailer is believed to be "Jihadi John", the killer who also appears in the execution videos of western hostages James Foley, Steven Sotloff, David Haines, Alan Henning and Peter Kassig.

Ishido also pleaded for the Japanese government to do all it could to save Kenji's life, revealing that he had left behind a new born baby to go to Syria in an attempt to save the man he is now being held hostage with.

"I cannot fathom what has been happening around me over the past three days," Ishido said. "I have been in sheer sadness and weeping all the way through."

Goto, a married father-of-four, travelled to the Islamic State's stronghold of Raqqa in October on a dangerous mission to rescue Yukawa, an eccentric self-styled security contractor, who had been kidnapped by the brutal Islamist group two months earlier.

Before leaving he left a video message in which he hinted he might possibly not make it back.

"It is very dangerous there, but no matter what happens, I will never hold a grudge against Syrians. I hope that this civil war will end as soon as possible," he said in the clip.