AMMAN (AFP, Reuters) - Jordan's military said on Friday that it was still awaiting proof that a warplane pilot threatened with execution by the Islamic State in Iraq and Syria (ISIS) group is alive.

ISIS had vowed to kill F-16 airman Muath al-Kasaesbeh by sunset on Thursday unless Amman handed over an Iraqi female extrenist in return for captured Japanese journalist Kenji Goto.

Jordan has demanded evidence that the pilot who crashed in Syria on December 24 is still alive before freeing would-be suicide bomber Sajida al-Rishawi who is on death row.

Jordan's army said state agencies were working to get information on the air force pilot, but offered no new word on his fate.

"State organs are working round the clock following up on the case of the pilot ... and in the event of any developments the information would be shared at the right time," army spokesman Colonel Mamdouh al Ameri said in a statement.