Qari Hikmatullah -- also spelled Hekmat -- and his bodyguard were killed in the northern province of Faryab on Thursday, US Forces-Afghanistan said in a statement.

The airstrike happened in Bal Chiragh district, the statement said. That borders Darzab district in Jowzjan province, which Afghan officials on Saturday had given as the location of the airstrike. Some had also said the incident happened on Friday.

Hikmatullah was a "native Uzbek" who previously belonged to other militant groups, including the Taliban, before joining IS's local franchise in northern Afghanistan, US Forces said.

The group has established a stronghold in Jowzjan after coming under intense pressure in the eastern province of Nangarhar.

Afghanistan's defence ministry said on Saturday that Hikmatullah was involved in or responsible for "deadly terrorist attacks" and had been replaced by Mawlawi Habib-ul-Rahman.

General John Nicholson, the top US commander in Afghanistan, vowed to kill "any successors" to Hikmatullah, adding that IS would be "eliminated".

Asked about the discrepancy in the location of the airstrike, defence ministry spokesman Mohammad Radmanish told AFP on Monday that some district borders were not marked clearly.

Afghan and US forces have ramped up airstrikes and ground offensives against IS fighters in Jowzjan in recent months as the group seeks to expand its foothold in the country.

Afghan security forces last month detained a French woman fighting for IS in Jowzjan. AFP has reported that French and Algerian fighters, some arriving from Syria, have joined IS in the restive province.

Also on Monday, at least six people were killed and another seven were wounded when explosives on a three-wheeled motorcycle exploded in the western province of Herat, officials said.