Mohammed Bugaighis died in an attack on a busy cafe that has been dubbed an 'assassination'
A veteran Libyan activist known for fighting corruption was one of four people killed in an explosion in the second city of Benghazi late on Saturday night, in what local media are dubbing an "assassination".
Mohammed Bugaighis, head of the Libyan International Organisation Against Corruption, died in an attack on a busy cafe in the east of the strife-torn country, officials confirmed on Sunday.
The attack also wounded at least 23 other people.
A spokesperson for forces allied to controversial field marshal Khalifa Haftar said the blast was caused by a mortar shell, which struck the al-Kish neighbourhood of Benghazi causing a group of cars to burst into flames.
However, other sources told Libya's al-Wasat daily that the blast was caused by a car bomb which targeted the Sanbal Cafe, one of the most popular coffee houses in the neighbourhood.
Investigators said on Sunday that they are beginning a probe into what caused the attack, and who could be behind it.
Bugaighis was known for supporting Haftar, and taking positions that could be seen as opposed to Islamist groups active in the country.
He has previously been a target for violence and assassination attempts - in 2014, unknown militants detonated explosives at his house in Benghazi.
However, he was not injured in the attack, as he was speaking live on air at a television studio elsewhere in the city at the time.
For two and a half years, Benghazi has seen bloody battles between forces led by Haftar and armed groups including militants from Islamic State and Ansar al-Sharia, which is close to al-Qaeda.
Haftar's forces have taken over much of Benghazi but have been unable to impose their control over the whole city, and still face pockets of resistance from dissident groups.
Libya has been mired in violence and political chaos since the 2011 uprising that toppled and killed longtime dictator Moamer Gaddafi.
The UN special envoy to Libya, Martin Kobler, condemned the latest attack on his official Twitter account.
The German diplomat wrote that Bugaighis was among two anti-corruption activists killed in the blast, and called for the culprits to be brought to justice.