ISLAMABAD (Reuters) - The Islamic State group on Thursday confirmed the death of its leader Abu Bakr al-Baghdadi in a voice message broadcast by its media wing, Furqan, days after the United States announced his death during a special military operation.

ISIS said in an audio recording of its spokesman Abu Hamza al-Qurashi that he had appointed Sheikh Abu Ibrahim al-Hashemi al-Qurashi to succeed Baghdadi.

He added that what he called the Islamic State Shura Council convened as soon as he confirmed that Baghdadi had been killed.

The United States has vowed more aggressive attacks than in Baghdadi's time, and called on ISIS followers to avenge their leaders.

There is little information about the successor to Baghdadi, who was appointed today as leader of the organization.

Qureshi also mourned Abu Hassan al-Muhajir, one of the group's most prominent leaders.

A senior State Department official confirmed on Monday the death of ISIS spokesman Abu Hassan al-Muhajir, a senior figure in the group, in another operation carried out by US forces after the killing of the group's leader.

The US official, who spoke to reporters on condition of anonymity, said the immigrant was killed in the city of Jarablus in Aleppo province in northern Syria.

The operation, which led to the "elimination of one of Baghdadi's top aides," was also carried out by US forces, the official said, adding that the SDF had a major role to play.