DHAKA: Islamic State militants say they will execute a Jordanian pilot "immediately" if Amman does not hand over a female suicide bomber by sunset Thursday (Jan 29), as Japan waits in anguish for news of a journalist the extremists are also holding.

In a new audio recording, a voice identifying itself as Japanese freelancer Kenji Goto says his captors will kill Maaz al-Kassasbeh if an Iraqi woman on death row in Jordan is not handed over by the end of the day.

"If Sajida al-Rishawi is not ready for exchange for my life at the Turkish border by Thursday sunset, 29th of January, Mosul time, the Jordanian pilot Maaz al-Kassasbeh will be killed immediately," Goto said, in an unverified audio message distributed by IS-linked Twitter accounts.

It was not clear from the message if either Goto or Kassasbeh would be freed. The recording was reported by monitoring group SITE Intelligence.

Japanese Prime Minister Shinzo Abe told parliament: "We are aware of the new message (and) are verifying (its authenticity)."

The apparent communication breaks an anxious silence from the extremists since their previous 24-hour deadline for Rishawi expired, around 1400 GMT Wednesday. Amman had offered to free the Iraqi woman, who was convicted for her part in 2005 triple-hotel bombings in the Jordanian capital that killed 60 people, if the IS group released their airman.

"Jordan is ready to release the prisoner Sajida al-Rishawi if the Jordanian pilot is freed unharmed," state television quoted a government spokesman as saying Wednesday. "From the start, the position of Jordan was to ensure the safety of our son, the pilot Maaz al-Kassasbeh," it added.

The government spokesman made no mention of Japanese hostage Goto.

BDST: 0952 HRS, JAN 29, 2015