The audio, partly dedicated to religious scriptures, came after several reports Baghdadi had been killed.
His last recording was in November 2016, two weeks after the start of the battle to recapture the city of Mosul from IS.
The date of the 46-minute recording released via the Al-Furqan news organisation was not clear.
But in it, Baghdadi makes an apparent reference to recent events including North Korean threats against Japan and United States and the recapture two months ago of Mosul by United States-backed Iraqi forces.
Since Baghdadi proclaimed the caliphate stretching across Iraq and Syria in 2014, Iraqi forces have retaken a string of cities in western and northern Iraq including Mosul, where he made his announcement from the city’s El Nuri mosque.
Western-backed Syrian forces are also thrusting into the eastern Syrian city of Raqqa, Islamic State’s operational headquarters from where it plotted many of the attacks that have killed hundreds of people around the world.
“Beware of retreat, or the feeling of defeat, beware of negotiations or surrender. Do not lay down your arms,” Baghdadi said, referring to followers in Iraq, Syria, Saudi Arabia, North Africa and elsewhere in Africa.
“Oh Soldiers of the Caliphate, fan the flames of war on your enemies, take it to them and besiege them in every corner, and stand fast and courageous.”
Baghdadi also referenced Western media, saying: “Oh soldiers of Islam in every location, increase blow after blow, and make the media centres of the infidels, and where they wage their intellectual wars, among your targets.”
Fall of Mosul
The fall of Mosul in July effectively marked the end of the Iraqi half of Baghdadi’s “caliphate” even though Islamic State continues to fight in some territory outside of Mosul, the largest city they came to control in both Iraq and Syria.
An IS branch in Libya was also defeated last year in the city of Sirte, where they had set up a North African beachhead in 2014. In Egypt’s northern Sinai, another affiliated militant group is still fighting Egyptian military forces.
“With God’s will and his strength, we are staying determined, patient…The abundance of killing will not stop us,” Baghdadi said in the audio recording.
Officials have said they believed it could take years to capture or kill Baghdadi as he is thought to be hiding in a vast swathe of sparsely-populated desert between Mosul and Raqqa, where attacking drones are easy to spot.
The US has offered a $25 million bounty for information that would locate Baghdadi.
Russia’s defence ministry said earlier this year it might have killed Baghdadi in an air strike on a gathering of IS commanders on the outskirts of Raqqa.
But US officials said they could not corroborate the death and other Western as well as Iraqi officials were sceptical.