ISIL has released an unverified audio recording that it said was by its leader Abu Bakr al-Baghdadi, who called on the armed group's followers to "resist the infidels".
The date of the 46-minute recording, released on Thursday via the ISIL-linked Al-Furqan news organisation, was not clear.
But in it, the apparent leader of the Islamic State of Iraq and the Levant (ISIL, also known as ISIS) group referred to the North Korean threats against Japan and the United States.
It is the first apparent communication from the elusive leader in almost year, during which the group has lost much of the territory it controlled in Iraq and Syria.
The audio release, much of which is dedicated to religious scriptures, comes amid growing speculation over al-Baghdadi's fate.
"The leaders of the Islamic State and its soldiers have realised that the path to ... victory is to be patient and resist the infidels," he said in the message.
In a statement to AFP news agency, a US intelligence official suggested the tape could well be real but added that it was still being verified.
"We are aware of the audio tape purported to be of Abu Bakr al-Baghdadi and are taking steps to examine it," the source said.
"While we have no reason to doubt its authenticity, we do not have verification at this point."
The armed group leader's last recorded speech was issued in early November 2016, two weeks after the start of the battle for the Iraqi city of Mosul, when he urged his followers to fight the "unbelievers" and "make their blood flow as rivers".
Meanwhile, the Islamic State group killed at least 58 Syrian government troops and militia as the jihadists put up fierce resistance to a Russian-backed offensive against some of its last bastions, a monitor said Friday.
Most of Thursday's dead came south of the desert town of Sukna, east of the ancient city of Palmyra, the Syrian Observatory for Human Rights said.
IS put out a statement claiming to have killed scores of regime fighters in the area and also released what it said was an audio recording of its leader Abu Bakr al-Baghdadi urging resistance, his first in months.
Syrian troops pushed through the vast desert that separates the main cities of the west from the Euphrates Valley this summer and broke a three-year IS siege of government enclaves in the eastern city of Deir Ezzor earlier this month.
Thursday's attacks targeted government forces around Deir Ezzor and on their supply lines through the Sukna area from the west, the Observatory said.
"The first attacks were carried out against checkpoints manned by loyalist troops in Al-Shula," a village near Deir Ezzor, the Britain-based monitoring group said.
"IS then carried out a series of attacks against checkpoints along the length of the motorway from Al-Shula to south of Sukna."
