Europe migrants, 40 were killed at a detention centre on the outskirts of the Libya capital Tripoli, the government officials say.
Some 80 people were injured at the centre, which the UN-backed government says was hit by an air strike.
Anti-government powers driven by warlord Gen Khalifa Haftar have blamed government powers for assaulting it.
The vast majority of the dead are accepted to be Africans, attempting to reach Europe on clandestine sea crossings from Libya.
Thousands of migrants are stopped and held in government-run detention centres.
The country has been torn by violence and division since long-time ruler Muammar Gaddafi was deposed and killed in 2011
Some 120 migrants were inside a hangar at the Tajoura Detention Centre which took a direct hit, emergency services spokesman Osama Ali told AFP news agency.
An official in the Libyan health ministry, Doctor Khalid Bin Attia, attended the scene of the strike and described the carnage.
“People were everywhere, the camp was destroyed, people are crying here, there is psychological trauma, the lights cut off,” he told BBC World Service.
“We couldn’t see the area very clear but just when the ambulance came, it was horrible, blood is everywhere, somebody’s guts in pieces.”
The UN refugee agency said it was “extremely concerned” at the news of the attack.
Who is to blame?
The UN-backed Government of National Accord (GNA), led by Prime Minister Fayez al-Sarraj, accused the self-styled Libyan National Army (LNA) of carrying out an air strike on the centre.
The “heinous crime” was “premeditated” and “precise”, it said.
The LNA – led by Gen Haftar – was fighting government forces in the area where the strike happened.
It had announced on Monday that it would start heavy air strikes on targets in Tripoli after “traditional means” of war had been exhausted.
The LNA said its warplanes had bombed a pro-government camp near the centre and pro-government forces had fired shells in response, hitting the migrant centre by accident.
Why is there war in Libya?
No authority has full control over Libya and the country is extremely unstable, torn between several political and military factions, the two most important of which are those led by Prime Minister Sarraj and Gen Haftar.
Gen Haftar started an offensive against the government in April.
The general has been active in Libyan politics for more than four decades and was one of Gadaffi’s close allies until a dispute in the late 1980s forced him to live in exile in the US.
After returning to Libya when the uprising began in 2011, he built up a power base in the east and has won some support from France, Egypt and the UAE.
Libyans have mixed feelings towards him due to his past association with Gadaffi and US connections, but do credit him for driving Islamist militants out of much of the city of Benghazi and its surroundings.
source :http:// bbc.com