PM condemns Japanese hostage killing

Prime Minister Tony Abbott has joined the global outrage over the reported murder of a Japanese hostage by the Islamic State extremist group, labelling it an "absolute atrocity".

The Japanese government has cast doubt on the authenticity of a new online video purporting to show the killing of Haruna Yukawa but US President Barack Obama issued a statement condemning "the brutal murder".

Mr Abbott said the apparent execution of the 42-year-old adventurer was further bad news from the Middle East.

"It seems one of the Japanese hostages has been executed by the Daesh death cult," the prime minister said in Canberra on Sunday.

"This is an absolute atrocity."

Mr Abbott sent his condolences to the man's family and that of a second hostage, journalist Kenji Goto.

"It's hard to imagine the anguish that (their) families would be going through," he said.

"And indeed, the anguish the people of Japan would now be suffering."

Labor leader Bill Shorten hoped the reports were unfounded.

"If this has happened, this is an act of bloodthirsty barbarity," he told reporters in Melbourne.

It highlighted the need for the world to stand up against gangsters, crooks and terrorists masquerading religious causes, he said.

"It is an unspeakable evil."

Mr Shorten also urged young Australian women not to join foreign conflicts for "misguided reasons".

"Do not go to these parts of the world," he said.

"It will end in tears."