Islamic State confirmed on Thursday that its leader Abu Bakr al-Baghdadi was killed in a weekend raid by US forces in northwestern Syria and vowed revenge against the United States.

Baghdadi, an Iraqi jihadist who rose from obscurity to become the head of the ultra-hard line group and declare himself “caliph” of all Muslims, died during the swoop by US special forces.

Islamic State (IS), which held swathes of Iraq and Syria from 2014-2017 before its self-styled caliphate disintegrated under US-led attacks, had previously been silent about Baghdadi’s status.

It confirmed his demise in an audio tape posted online and said a successor it identified only as Abu Ibrahim al-Hashemi al-Quraishi had been appointed.

Aymenn al-Tamimi, a researcher at Swansea University focusing on Islamic State, said the name was unknown but could refer to a leading figure in Islamic State called Hajj Abdullah whom the US State Department had identified as a possible successor to Baghdadi.

Whether the loss of its leader will in itself affect the group’s capabilities is open to debate. Even if it does face difficulties in the leadership transition, the underlying ideology and the sectarian hatred it promoted remains attractive to many, analysts say.