Islamic State militants have released what appears to be an audio recording of their leader, Abu Bakr al-Baghdadi.
A speaker who sounds like the IS leader seems to refer to recent North Korean threats against Japan and the US.
He also talks of battles for IS strongholds like Mosul, which was regained by Iraqi forces in July.
Baghdadi has not been seen in public since July 2014, leading to much speculation about his fate.
A defence department spokesman told the BBC: "We are aware of the audio tape purported to be of Abu Bakr al-Baghdadi and are taking steps to examine it. While we have no reason to doubt its authenticity, we do not have verification at this point."