A senior "Islamic State of Iraq and Syria" (ISIS) leader who oversaw the production of mustard gas used in attacks on Iraqi forces has been arrested, the Iraqi Ministry of Defence said Wednesday (May 20th).

Abdul Naser Qardash, whose real name is Taha Abdul Rahim Abdullah Bakr al-Ghassani, was born in Tal Afar in 1967 and lived in the neighbourhood of Mushairafa in Mosul.

Abdul Naser Qardash "is not the same as Abdullah Qardash, who assumed the leadership of ISIS after Abu Bakr al-Baghdadi was killed in October", intelligence expert Fadel Abu Ragheef told Diyaruna.

The Iraqi Intelligence Service arrested Qardash after extensively tracking his movements in co-ordination with the Syrian Democratic Forces (SDF), he said.

The arrest "took place months ago, but was not announced until investigations were completed on the terrorist cases Qardash was involved in", he said.

'Dangerous leader'

Qardash is a "dangerous leader who has played a major role in the manufacture, development and equipping of chemical weapons for [ISIS]", said Abu Ragheef, who noted that the militant is a bomb-making expert.

"He is a terrorist figure of the highest order who has been involved in dozens, if not hundreds of attacks and bombings in the last decade in Kirkuk, Mosul and Salaheddine province," Abu Ragheef said.

Qardash has "held several senior positions during al-Baghdadi's leadership of [ISIS], including wali of Mosul, Kirkuk and al-Jazeera, as well as wali of the Syrian provinces of al-Hasakeh, Deir Ezzor and al-Raqa", he said.

He also oversaw manufacturing and development, setting up factories to supply weapons, explosives and pistols with silencers to ISIS's wilayat, he said.

Thanks to Qardash's close relationship with al-Baghdadi -- reports indicate they met over a hundred times -- he was considered the top commander who oversaw the battle of Kobani and the offensives to control Palmyra, Aleppo and Damascus.

He also oversaw the battles in al-Bab, and finally the battle of al-Baghouz that saw the terror group defeated.

He was also assigned by al-Baghdadi to conduct negotiations between ISIS and other extremist factions and groups, said Abu Ragheef.

The last position he held prior to his arrest was "the position of deputy to [ISIS leader] Abdullah Qardash", according to Abu Ragheef.

His arrest is a "heavy blow for the group", but the ISIS threat remains, he said, which calls for continued security operations to end the group's threat once and for all.