Twin bomb blasts struck a mosque in Benghazi in eastern Libya on Friday, killing at least one person and wounding 149 in the latest attack to target worshippers in the city.
The attack in the city of Benghazi, Libya, occurred place during Friday's prayers at a small mosque in Majouri district and was remotely detonated by mobile phone according to residents.
The incident comes weeks after a double auto bombing in Benghazi killed at least 35 people.
"This heinous act should not provide a justification for revenge attacks".
"Direct or indiscriminate attacks against civilians are prohibited under worldwide humanitarian law and constitute war crimes", the mission added, calling for "prompt, impartial investigations to bring perpetrators to justice".
Libya has been plagued by unrest and political division since the uprising that toppled its former leader Muammar Gaddafi's regime in 2011.
The country has been since split between rival governments and militias.
The LNA was battling Islamists, including some linked to Islamic State and Al Qaeda, as well as other opponents until late previous year in the Mediterranean port city.
Fears over potential reprisals are heightened by the reported summary execution of around 10 jihadist prisoners by a commander loyal to Haftar following last month's bombings.
Chief of a Special Investigation Unit, Ahmed al-Fituri, attached to the General Command of East Libyan security forces, was among the casualties.
He does not recognise the UN-backed Government based in the western capital Tripoli.
The United Nations has been trying to mediate for years, hoping elections can help stabilize Libya.
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