AMMAN (AFP) - Jordan said Wednesday it was still awaiting proof from the Islamic State in Iraq and Syria (ISIS) militant group that a captured Jordanian pilot was alive, hours after the country offered a prisoner exchange.

"We asked a while ago for proof that hero Maaz (al-Kassasbeh) is alive but we have not received anything," Foreign Minister Nasser Judeh wrote on Twitter shortly before 1500 GMT (11pm Singapore time).

About an hour earlier he denied that Iraqi female militant Sajida al-Rishawi had already been freed in exchange for the pilot.

ISIS, in a video released Tuesday, threatened to kill Kassasbeh and Japanese hostage Kenji Goto unless Jordan released Rishawi within 24 hours.

According to Tokyo the deadline expired at about 1400 GMT Wednesday.

Rishawi has been on death row since 2006 for her part in triple hotel bombings in Amman that killed 60 people.