By his captors' past form, journalist Jumpei Yasuda's plight could be drawn out. It is thought he is being held by al-Qaida's Syria wing, the Nusra Front, possibly for ransom.

"Jabhat al-Nusra usually make use of hostages to conduct prisoner swaps or gain benefits, which might be financial," said Clive Williams, a terrorism expert at the Australian National University in Canberra. "They do not go in for the execution of prisoners or the kind of brutality against some prisoners associated with the Islamic State — although even IS has released more Western prisoners than they have executed.

"IS usually only execute Western prisoners from countries that won't negotiate ransoms, i.e. mainly the U.S. and U.K., but they also executed Kenji Goto and Haruna Yukawa when Japan wasn't cooperative enough, in their view," Williams added.