Japan and Jordan were working closely on Friday to find out what had happened to two of their nationals being held by the Islamic State (IS) terrorist group, after a deadline passed for the release of a would-be suicide bomber being held on death row in Jordanian capital Amman.

Japanese Prime Minister Shinzo Abe said every effort was being made to secure the release of war journalist Kenji Goto.

"We are gathering and analyzing information while asking for cooperation from Jordan and other countries, making every effort to free Kenji Goto," he told a parliamentary panel.

Jordan said on Thursday it was still holding the aspiring bomber, an Iraqi woman, prisoner as a deadline set by IS militants for her release passed. The militants had threatened to kill a Jordanian pilot unless she was handed over by sunset.

An audio message purportedly from Goto said the pilot would be killed if Jordan did not free Sajida al-Rishawi, in jail for her role in a 2005 suicide bomb attack that killed 60 people in Amman.

The message extended a previous deadline set on Tuesday in which Goto said he would be killed within 24 hours if Rishawi was not freed.

Japanese Chief Cabinet Secretary Yoshihide Suga said late on Friday that Tokyo was doing everything it could, but declined to answer whether negotiations had stalled and if there was any progress.

"We are doing the things we have to, one after the other, steadily," he told a news conference.

The hostage crisis comes as IS, which has already released videos showing the beheadings of five Western hostages, is coming under increased military pressure from US-led air strikes and by Kurdish and Iraqi troops pushing to reverse the Islamist group's territorial gains in Iraq and Syria.

About an hour before the new deadline was due to pass on Thursday, government spokesperson Mohammad al-Momani said Jordan was still holding Rishawi. "We want proof ... that the pilot is alive so that we can proceed with what we said yesterday; exchanging the prisoner with our pilot," Momani told Reuters.

The pilot, Maaz al-Kasaesbeh, was captured after his jet crashed in northeastern Syria in December during a bombing mission against IS.

Momani said separately that Jordan was coordinating with Japanese authorities in an effort to secure the release of Goto.

In the latest audio recording purportedly of Goto, he said that Kasaesbeh would be killed "immediately" if Rishawi was not at the Turkish border by sunset on Thursday, Iraq time, ready to be exchanged for the Japanese hostage. That was some time around 1430 GMT on Thursday.

The implication that the pilot would not be part of an exchange deal has left Jordan in a difficult position.

Jordan's military said on Friday again that it was still awaiting proof that Kasaesbeh is safe. "Jordan has so far received no information that proves the pilot Maaz al-Kassasbeh is safe and sound," military spokesman Mamdoh al-Ameri told AFP.

Jordanian comments have raised concerns in Japan that Goto might not be part of any deal between Amman and IS.

While IS threatened Kassasbeh's life, it was not clear from the latest message if the jihadist group was ready to free him as part of an exchange.

Japanese Foreign Minister Fumio Kishida told journalists that Tokyo had asked Jordan to beef up protection of its diplomats in the country on Friday, the birthday of Jordanian King Abdullah.

The hostage crisis erupted after Abe announced in Cairo $200 million in non-military aid for countries opposing IS, but his government has rejected suggestions it acted rashly and stressed the assistance was humanitarian.