There is a "state of deadlock" in negotiations to release a journalist held by Islamic State (IS) militants, according to a top Japanese diplomat.

Japan's deputy foreign minister Yasuhide Nakayama made the comments in the Jordanian capital Amman, where he is leading Tokyo's team attempting to secure the freedom of veteran war reporter Kenji Goto.

Mr Goto (47) has appeared in videos released by IS in which his fate has been linked to another hostage, Jordanian fighter pilot Lt Muath al Kasaesbeh.

Speaking late on Friday night, Yasuhide Nakayama said: "Staying vigilant, we will continue analysing and examining information as the government is making concerted efforts together."

Jordan and Japan have held indirect negotiations with the militants, who control around a third of Iraq and Syria, for release of the men in exchange for a jailed jihadist.

But Jordan has demanded evidence that the airman who crashed in Syria on December 24th is still alive before freeing the would-be suicide bomber, who is on death row.

IS had said it would kill Jordan's captured pilot by sunset on Thursday unless Iraqi jihadist Sajida al Rishawi was released.

Some security experts believe the stalled negotiations are being orchestrated by IS to ferment unrest in Jordan, where protests have been aimed at ruler King Abdullah over the pilot's plight.

Earlier this month, IS released video of Mr Goto and another Japanese hostage - private security firm worker Haruna Yukawa.

It threatened to kill the men unless a US$200m (€177m) ransom was paid.

Last week Japanese Prime Minister Shinzo Abe slammed "an outrageous and unforgivable act" after a video reportedly showing an image of Mr Goto holding a picture of a beheaded Mr Yukawa was posted online.

The family of Mr Goto has made public pleas to Mr Abe to negotiate for his safe release.

Mr Goto went into Syria in late October seeking to secure Mr Yukawa's release, according to friends and business associates.