The United Nations-brokered administration in Libya accused warlord Khalifa Haftar’s forces, fighting on behalf of the breakaway government in the eastern part of the country, of launching an airstrike on Wednesday that struck a migrant detention center in Tripoli, reportedly killing at least 44 people and wounding over 130.

While some news outlets report that the attack took place early Wednesday, others and the U.N. High Commissioner for Refugees (UNHCR) say it was carried out late Tuesday night. 

Charlie Yaxley, a spokesperson for UNHCR, indicated that the incident could have been avoided, telling the Agence France-Presse (AFP) that the agency asked for the facility to be evacuated a few weeks ago after “a near miss from a similar airstrike.”

“We are horrified at the deaths,” he told AFP.

In a statement issued Wednesday, the internationally recognized Government of National Accord (GNA) based in Tripoli lambasted “war criminal Khalifa Haftar,” holding him responsible for what it described as a “heinous crime,” referring to the attack on the migrant center, the AFP notes in a separate article.

The GNA accused Gen. Haftar’s Libyan National Army (LNA) of having conducted a “premeditated” and “precise” attack on the detention center.

Although no one has claimed responsibility for the attack so far, AFP notes that pro-Haftar media acknowledged a “series of air raids” in Tripoli’s Tajoura neighborhood Tuesday night.

On Monday, Haftar’s troops announced plans to launch “heavy airstrikes” on pro-GNA fighters in Tripoli after they lost the strategic town of Gharyan, considered a key supply route for the LNA.

The strike “clearly could constitute a war crime”, Ghassan Salame, the U.N. envoy to Libya, said according to AFP.

“It killed, by surprise, innocent people whose dire conditions forced them to be in that shelter,” he added.

In April, the LNA launched an offensive to take the capital of Tripoli from the U.N.-backed administration of Prime Minister Fayez al-Serraj headquartered there.

The World Health Organization revealed on June 25 that the fighting in Tripoli had already killed 739 people and injured 4,407.

On Wednesday, the LNA targeted a pro-GNA militia camp near a migrant detention center in Tripoli’s Tajoura neighborhood.

AP reports:

An airstrike hit a detention center for migrants in the Libyan capital early Wednesday, killing at least 44 people and wounding more than 130, the U.N. mission to the war-torn country said. …Footage circulating online and said to be from inside the migrant detention center showed blood and body parts mixed with rubble and migrants’ belongings.

LNA troops reportedly struck a workshop housing weapons and vehicles, and the adjacent detention center holding the migrants.

The aid group Doctors Without Borders revealed that the bombed cell at the facility housed 126 migrants.

On Twitter, the aid group reacted to the “horrifying events,” saying “refugees and migrants trapped in Tripoli detention centers must be immediately evacuated”.

AP learned from the U.N. refugee agency in Libya that the facility held a total of 616 migrants and refugees.

The agency condemned the attack on the detention center and called for an immediate end to European Union-backed efforts to return migrants to Libya, which often leaves them at the mercy of unscrupulous traffickers or stranded in squalid prisons near combat zones.

Via Twitter, the U.N. refugee agency expressed concerns about Wednesday’s attack.

“UNCHR is extremely concerned about news of air strikes targeting Tajoura detention centre east of Tripoli, and accounts of refugees and migrants deceased,” it tweeted. “Civilians should never be a target”:

Human rights groups and the U.N. have revealed that migrants held in Libya face horrifying abuses at the hands of their captors, including slavery.

“The plight of migrants has worsened since Haftar launched an offensive against Tripoli,” AFP points out.

Speaking on condition of anonymity for fear of reprisals, two migrants told AP that most of the detainees at the migrant center allegedly targeted by the LNA this week are Sudanese and Moroccans.

Detention centers in Libya run by militias accused of torture and other human rights violations are reportedly housing at least 6,000 migrants from Eritrea, Ethiopia, Somalia, Sudan, and other African countries.

The U.N. refugee agency has determined that the fighting in and around Tripoli threatens more than 3,300 migrants who remain arbitrarily detained, and held in detention centers near the combat zone “in conditions that can only be described as inhumane.”

With the help of Russia, France, the United Arab Emirates (UAE), and Egypt, Haftar and his forces have conquered much of Libya, particularly territory in the eastern and southern parts of the country.

AP describes Haftar’s rivals, mainly backed by Qatar and Turkey, as Islamists.

Libya descended into political and security chaos following the 2011 U.S.-backed overthrow and execution of dictator Muammar Gaddafi, with rival governments and their militias competing for power as jihadi groups cultivate their presence in the oil-rich North African country.

Haftar’s foreign supporters believe he can restore political stability and defeat the jihadi groups in the country.