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 today 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.

Japan's Chief Cabinet Secretary Yoshihide Suga told journalists the recording seemed genuine.
"We are in the process of confirming it, but it is highly probable that the voice is Goto's," he said.
The apparent communication breaks an anxious silence from the extremists since their previous 24-hour deadline for Rishawi expired at around 1930 IST on Wednesday.
Amman had offered to free the Iraqi woman, who was convicted for her part in triple-hotel bombings in the Jordanian capital in 2005 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.
"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.
Jordanian Foreign Minister Nasser Judeh wrote on Twitter shortly before 2030 IST that his country was still awaiting confirmation that the pilot was safe.
On Wednesday passed in a maelstrom of conflicting reports on the fate of the three key players, complicated by linguistic and cultural misunderstandings, and by the high stakes on all
The atmosphere was tense in Jordan, where the country's involvement in the US-led air raids against IS positions is contentious.
The downing on December 24 of Kassasbeh's F-16 fighter jet over northern Syria and his subsequent capture and humiliation by jihadists exacerbated the situation. This week the pilot's father begged the government to save his son "at any price".


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