Isis's senior leader in Libya, Abu Nabil, was killed in a US airstrike last month, the Pentagon has confirmed.
The strike on a compound in Derna took place on 13 November, before the terrorist attacks in Paris later that day.
Pentagon spokesman Peter Cook said the strike showed Isis leaders would be targeted "wherever they operate".
How big is Isis in Syria?
Isis is one of several militia groups trying to take control amid the fragile political situation in Libya, which has existed since the overthrow of Colonel Muammar Gaddafi four years ago.
There is currently no functioning government in Libya.
The jihadist group controls the city of Sirte, the birthplace of Colonel Gaddafi, which lies between the capital city of Tripoli and Benghazi.
It is the closest territory the militant group controls to mainland Europe.
How much will Abu Nabil's death affect Isis operations in Libya?
Nabil is believed to be a long-term al-Qaeda militant who previously operated in Iraq.
He is suspected of appearing in an Isis video, which showed the brutal beach murders of kidnapped Coptic Christians. The film included threats of future attacks against "people of the cross".
According to Pentagon spokesman Peter Cook, the death of Nabil will limit the ambitions of Isis in Libya.
In a statement released 14 November, Mr Cook explained: "Nabil’s death will degrade Isil’s ability to meet the group’s objectives in Libya, including recruiting new Isil members, establishing bases in Libya, and planning external attacks on the United States."
However, the extent to which Nabil's death damages Isis operations in Libya remains to be seen.
Earlier this month, a United Nations report revealed Isis is preparing a "retreat zone" in the country, as coalition air strikes pound the group's strongholds in Iraq and Syria
The UN report says the group's central command in Iraq and Syria see Libya as the best opportunity to expand its caliphate, viewing the country as "a potential retreat and operational zone for Isis fighters unable to reach the Middle East".
It says the group in Libya had grown from 200 fighters to around 2,000 since it announced its branch in the country.
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