US president Barack Obama has led worldwide condemnation of the killing of a Japanese journalist by Islamic State (IS) militants, calling it a "heinous murder".

The agony of the families of a captured journalist and fighter pilot is continuing after a sunset deadline for a possible prisoner swap allegedly set by their Islamic State (IS) kidnappers passed with no clue whether they are still alive.

Experts are examining a recorded message said to have been from hostage Kenji Goto, extending the deadline for Jordan's prisoner-swap release of an Iraqi would-be suicide bomber linked to al Qaida.