The Islamic State group said Wednesday that its leader Abu Hasan al-Hashimi al-Qurashi has been killed in battle and announced a replacement.
A spokesman for the group said Hashimi, an Iraqi, was killed "in combat with enemies of God," without elaborating on the date of his death or the circumstances.
Speaking in an audio message, the spokesman identified the group's new leader as Abu al-Hussein al-Husseini al-Qurashi.
Qurashi refers to a tribe of the Prophet Muhammed, from whom IS leaders must claim descent.
The spokesman did not provide details on the new leader, but said he was a "veteran" jihadist and called on all groups loyal to IS to pledge their allegiance.
After a meteoric rise in Iraq and Syria in 2014 that saw it conquer vast swathes of territory, IS saw its self-proclaimed "caliphate" collapse under a wave of offensives.
It was defeated in Iraq in 2017 and in Syria two years later, but sleeper cells of the extremist group still carry out attacks in both countries.
IS's previous leader, Abu Ibrahim al-Qurashi, was killed in February this year in a US raid in Idlib province in northern Syria.
His predecessor Abu Bakr al-Baghdadi was killed, also in Idlib, in October 2019.
Hassan Hassan, who authored a book on IS, said one "unprecedented" but possible scenario was that the Hashimi "was killed 'accidentally' during a raid or fighting without him being known to whoever killed him".
In October this year, US forces killed a "senior" IS member in a pre-dawn raid in northeastern Syria, the US military's Central Command said at the time.
It said a later air strike had killed two other senior IS members.
The US leads a military coalition battling IS in Syria.
In July, the Pentagon said it had killed Syria's top IS jihadist in a drone strike in the north of the country.
US Central Command said he had been "one of the top five" IS leaders.
Turkey in September said security forces had arrested a "senior executive" of IS known as Abu Zeyd, whose real name was Bashar Khattab Ghazal al-Sumaidai.
Turkish media said there were some indications Sumaidai might have been the IS leader.