It is the highest publicly reported toll of an air strike or shelling since eastern forces loyal to warlord Khalifa Haftar three months ago launched an offensive to take the capital held by the internationally-recognised government.
An air strike hit a detention centre for migrants near the Libyan capital early on Wednesday, killing at least 44 people and wounding more than 130, the UN mission to the war-torn country said.
The air strike raises further concerns about the European Union's policy of partnering with Libyan militias to prevent migrants from crossing the Mediterranean, which often leaves them at the mercy of brutal traffickers or stranded in squalid detention centres near the front lines.
It wasn't immediately clear who was responsible for the strike but some suspected involvement by foreign countries allied with Khalifa Haftar, the warlord whose forces launched an offensive on Tripoli in April.
Countries assisting Haftar include the United Arab Emirates, Egypt and Russia.
The Tripoli-based government blamed his self-styled militia, called the Libyan National Army, for the air strike and called for the UN to investigate.
The appalling toll in injuries and lives from Tuesday night’s attack east of Tripoli at the Tajoura Detention Centre speaks to the deep concerns, expressed repeatedly by UNHCR and IOM, over the safety of people in detention centres. pic.twitter.com/gSwX3x7VVJ— UNHCR Libya (@UNHCRLibya) July 3, 2019
Death toll expected to rise
A spokesman for Haftar's forces did not immediately answer phone calls and messages seeking comment.
Local media reported the LNA had launched air strikes against a militia camp near the detention centre in Tripoli's Tajoura neighbourhood.
Footage circulating online and said to be from inside the migrant detention centre showed blood and body parts mixed with rubble and migrants' belongings.
The air strike hit a workshop housing weapons and vehicles and an adjacent hangar where around 150 migrants were being held, mostly Sudanese and Moroccans, according to two migrants who spoke to The Associated Press on condition of anonymity for fear of reprisal.
The migrants said three or four survived unharmed and about 20 were wounded. They said the rest were killed, indicating the final death toll could be much higher.
Doctors Without Borders said the detention cell that was destroyed held 126 migrants.
The aid group's Libya medical coordinator, Prince Alfani, said teams visited the centre just hours before the air strike. He said survivors fear for their lives, and he called for the immediate evacuation of the detention centres.
The UN refugee agency also condemned the air strike and called for an immediate end to efforts to return migrants to Libya.
The International Organization for Migration also condemned the attack.
🔴IOM and UNHCR strongly condemn the attack in Tajoura detention centre and any attack on civilian life. We also call for an immediate end to detention of migrants and refugees.https://t.co/mkApDVntw2 pic.twitter.com/R0sX9d5P3N— IOM Libya (@IOM_Libya) July 3, 2019
Migrants caught up in Tripoli fighting
UNHCR spokesman Charlie Yaxley noted that the agency had warned less than two months ago that anyone inside the Tajoura detention centre was at risk of being caught in the fighting around Tripoli.
Then, an air strike that hit nearby wounded two migrants.
Yaxley said UNHCR is sending medical teams to the site after the latest air strike.
The head of the African Union, Moussa Faki Mahamat, also condemned the strike. He called for an independent investigation and said those responsible for the "horrific crime" should be held to account.
The LNA launched an offensive against the weak Tripoli-based government in April.
Hafter's forces control much of Libya's east and south but suffered a significant blow last week when militias allied with the Tripoli government reclaimed the strategic town of Gharyan, about 100 kilometres (62 miles) from the capital.
Gharyan had been a key LNA supply route.
Haftar's forces have targeted positions in Tajoura with air strikes in recent weeks. The LNA said on Monday it had begun an air campaign on rival forces in Tripoli after it lost control of Gharyan.
Haftar's foreign support
Haftar's forces boast MiG fighter jets supplied by neighbouring Egypt, as well as drones, attack helicopters and mine-resistant vehicles. It was not immediately clear what munitions were used in the air strike early on Wednesday.
Oded Berkowitz, a security analyst focused on the Libyan conflict, said Haftar's LNA flies "a handful of obsolete aircraft" that are "in poor condition."
He said it has received spare parts from Egypt and possibly Russia, as well as decommissioned aircraft from both countries.
"Egypt and the UAE have been conducting air operations on behalf of the LNA, but there are no indications that the UAE transferred aircraft to the LNA," he said.
Fathi Bashagha, the interior minister of the Tripoli-based government, claimed that foreign countries allied with Haftar were behind the attack.
He told The Associated Press that Haftar's foreign backers "went mad" after his forces lost Gharyan.
He did not name any countries or provide evidence to support his claim. He also denied any weapons were being stored at the detention facility.
The fighting for Tripoli has threatened to plunge Libya into another bout of violence on the scale of the 2011 conflict that ousted longtime leader Muammar Gaddafi and led to his death.
Haftar says he is determined to restore stability to the North African country.
He is backed by Egypt, the United Arab Emirates and Saudi Arabia while his rivals are supported by Turkey and Qatar.
His campaign against militants across Libya since 2014 won him growing international support from world leaders who are concerned that Libya has become a haven for armed groups and a major conduit for migrants bound for Europe.
His opponents, however, view him as an aspiring autocrat and fear a return to one-man rule.
Libya became a major crossing point for migrants to Europe after Gadhafi's overthrow, when the North African nation was thrown into chaos, armed militias proliferated and central authority fell apart.
At least 6,000 migrants from Eritrea, Ethiopia, Somalia, Sudan and other nations are locked in dozens of detention facilities in Libya run by militias accused of torture and other abuses.
Most of the migrants were apprehended by European Union-funded and -trained Libyan coast guards while trying to cross the Mediterranean Sea to Europe.
The detention centres have limited food and other supplies for the migrants, who often end up there after arduous journeys at the mercy of abusive traffickers who hold them for ransom money from families back home.
The UN refugee agency has said that more than 3,000 migrants are in danger because they are held in detention centres close to the front lines.