One of the top ISIS spokesmen Abu Muhammad al-Adnani was killed while observing military operation in the Syrian province, ISIS told on Tuesday.

The announcement of ISIS group came after a US official said in the US led coalition air strike in Aleppo, an ISIS senior leader was targeted.

ISIS news agency Amaq said, “Sheikh Abu Muhammad al-Adnani, the spokesman of the ISIS, was martyred while surveying operations to repel the military campaigns against Aleppo”. It also stated that Abu Muhammad had died after a “long voyage crowned by sacrifice” and he swore ‘revenge’ at the hands of a “new generation born unto the Islamic States”.

Jihadist expert Romain Caillet affirmed Abu Muhammad al-Adnani will always be the one who in June 2014 announced the ‘restoration of the caliphate’.  According to the analysts, he was a key figure of the militant group.

He was ISIS’s No. 2 commander, its director of main propagandist and external operations. Abu Muhammad originally belonged from the western Syrian region of Idlib and joined the jihadist group in Iraq.

The US earlier announced a $5 million bounty on Adnani’s head and the ISIS spokesman was under US surveillance. A US official said that under a program called “Nomad Shadow” the US has been providing intelligence on the targets to Turkey.

Pentagon spokesman Peter Cook said in a statement that near Al Bab, Syria the alliance forces conducted a precision strike and targeting one of the ISIS’s most senior leader Abu Muhammad al-Adnani. “We are still assessing the results of the strike, but al-Adnani’s removal from the battlefield would mark another significant blow to [ISIS].”

In 2003 after he crossed the border of his native place Syria, Adnani was one of the first foreign fighters who opposed the US Coalition Forces in Iraq.

He was captured in 2005 and taken into custody at a US military camp, but in 2010 he was freed. After he released from the camp he then became the chief ISIS spokesman. By 2014 he had assumed a top operational role. In August 2014, US declared him a “specially designated global terrorist”.

Two other top ISIS officials, No.3 Omar al-Shishani and finance minister Haji Iman were also killed in this year. Co-founder of Flashpoint Laith Alkhouri stated that the death of the ISIS spokesman is a big blow for ISIS. He added that his killing may not break the back of ISIS but it could break the confidence of the fighters who idealized him.

Adnani was responsible for crafting the IS’s caliphate message and distributing the highly violent propaganda videos strengthening the ISIS’s global image across the Middle East and in different places.