Islamic State says one of its prominent field commanders has been killed in fighting in Libya.

The extremist group said Ahmed al-Ruwaysi, also known as Abu Zakariya al-Tunisi, was killed in clashes in the Libyan city of Sirte.

The 166th Battalion, a militia loyal to the unelected and self-proclaimed Libyan government in Tripoli, is fighting to seize control of Sirte from IS’s Libyan affiliate.

Libya’s elected and internationally recognised parliament has been forced from the capital and meets in the eastern city of Tobruk.

Al-Tunisi, according to the IS eulogy, planned and participated in the 2013 assassinations of two prominent left-wing Tunisian politicians, Mohammed Brahmi and Chokri Belaid.

Tunisian Interior Ministry spokesman Mohammed Ali Aroui told the state news agency that al-Ruwaysi’s death had been confirmed through “scientific means” and in co-ordination with Libyan authorities.

The 48-year-old was considered the mastermind of a string of attacks carried out in Tunisia by the radical Ansar al-Shariah movement, including the 2013 assassinations of Belaid and Brahmi.

Their deaths plunged Tunisia into a political crisis that eventually led to the resignation of the elected Islamist government.

Ansar al-Shariah founder Seifallah Ben Hassine has been implicated in the September 2012 assault on the US embassy in Tunis which resulted in severe property damage and the death of four protesters when security forces intervened.

Ben Hassine and al-Ruwaysi fled to Libya where they began fighting under the banner of the Islamic State group, which already controls about a third of Syria and Iraq in a self-declared caliphate.

An estimated 3,000 Tunisians have left the country to fight with extremist groups. Interior Ministry officials said 60 Tunisians had been killed so far in Syria.

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