Motaz Agouri, an official at Benghazi security directorate's media office, said the explosion took place during Friday prayers inside the Saad Ibn Ibada mosque in Benghazi's busy Berka district.
At least one person has been feared killed while more than 50 others have been injured in a bomb blast at a mosque in Libya's eastern city of Benghazi. Twin vehicle bomb attacks hit a mosque in Benghazi's Salmani district two weeks ago, killing 34 people and injuring more than 100 others.
The devices, placed inside bags, appear to have been activated remotely using a mobile phone, a military source said.
Late last month, a double car-bombing in the same city claimed the lives of at least 34 people and injured dozens more. "Prompt, impartial investigations should bring perpetrators to justice", the group said. The LNA has been battling Islamists, including some linked to Daesh and al-Qaeda.
Haftar, a possible contender in national elections that could be held by the end of 2018, has built his reputation on delivering stability in Benghazi and beyond, promising to halt the anarchy that ensued after a NATO-backed uprising ended Moammar Gadhafi's rule almost seven years ago.
Mr al-Werfalli is wanted by the ICC for allegedly carrying out a number of similar killings.
The UN-backed government in Tripoli also condemned the bombing, advocating "joint efforts to fight terrorism and those who threaten the safety and security of the country, and bring them to justice".
The North African nation has had competing governments aligned with rival military factions based in Tripoli and the east since 2014.