The UN on Wednesday demanded an independent inquiry after a military strike on a Libyan detention centre for migrants killed 44 people, including women and children, and wounded 130.
UN Secretary General Antonio Guterres described the attack east of Tripoli as horrendous. Rival sides in the Libyan conflict blamed each other for it.
The Tajoura detention centre was hit late on Tuesday, but it was not immediately clear if the cause was an air strike or an artillery shell.
Mr Guterres said the exact co-ordinates of the centre had been provided to the warring parties to ensure it was avoided.
Ghassan Salame, the Secretary General’s special envoy to Libya, said the attack could constitute a war crime and he urged the international community to punish those who ordered, carried out and provided arms for the strike.
It was the second time the centre had been attacked.
“The absurdity of this ongoing war today has led this odious, bloody carnage to its most hideous and most tragic consequences,” Mr Salame said.
It was by far the biggest single-day casualty toll since fighting broke out in Tripoli three months ago, when Field Marshal Khalifa Haftar launched an offensive on the capital days before UN-sponsored peace talks were due to start.
Field Marshal Haftar, leader of the Libyan National Army, has been fighting militias loyal to the UN-recognised Government of National Accord.
“There were bodies, blood and pieces of flesh everywhere,” Moroccan survivor Al Mahdi Hafyan, 26, told AFP from a hospital bed where he was being treated for a leg wound.
The government blamed the LNA for the air strike and called for the UN support mission in Libya to investigate.
An LNA official denied that the force had hit the detention centre, saying militias allied to Tripoli had shelled it after a precision air strike by the LNA on a military camp.
Local media reported LNA air strikes against a militia camp near the detention centre.
The Security Council has been divided on how to address the Libyan conflict, with the US resisting calls from other leading countries for a ceasefire and return to political dialogue.
"The Americans have been reluctant to act, until this point at least," a senior diplomat told The National before an emergency meeting of the council.
But even before Tuesday’s deaths, moves were afoot on the council to push again for a ceasefire amid mounting worries that an influx of weapons to both sides, in contravention of a UN arms embargo, could fuel the conflict.
About 600 migrants and refugees were held in the Tajoura centre, compound head Noureddine Al Grifi said, and other people were wounded in another hangar.
The US State Department sent condolences to the families of those killed and urged all sides to return to the peace process.
"This tragic and needless loss of life, which impacted one of the most vulnerable populations, underscores the urgent need for all Libyan parties to de-escalate fighting in Tripoli and return to the political process, which is the only viable path to lasting peace and stability in Libya," the department read.
The United Nations Network on Migration said the attack was an appalling breach of international law that showed the need to safeguard civilians from conflict.
“It also highlights the additional plight of the thousands of migrant women, men, girls and boys arbitrarily deprived of their liberty in detention centres across Libya, where the UN has documented degrading, inhumane and unsafe conditions, including torture, ill-treatment, forced labour, enforced disappearance, rape, and a lack of access to food and essential medical care, among other serious human rights violations,” a statement said.
UN refugee agency spokesman Charlie Yaxley said in Geneva that it had asked to have the centre evacuated a few weeks ago after “a near miss from a similar air strike”.
Field Marshal Haftar’s forces control much of the country’s east and south but were dealt a blow last week when militias allied with the Tripoli government reclaimed the strategic town of Gharyan, about 100 kilometres from the capital.
Gharyan had been a critical supply route for LNA forces.
Many camps for militias loosely allied with the UN-supported government are in Tajoura, and LNA forces have attacked their camps with air strikes in the past weeks.
The LNA said on Monday that it had begun an air campaign against rival fighters in Tripoli after it lost control of Gharyan.
The fighting for Tripoli has threatened to plunge Libya into violence on the scale of the 2011 conflict that ousted dictator Muammar Qaddafi.
