International bodies such as the United Nations and the European Union on Thursday called for an independent inquiry into an airstrike on a detention centre in Libyan capital, Tripoli in which 44 migrants were killed, AFP reported.

United Nations chief Antonio Guterres called the attack horrendous amid speculations that the United Nations Security Council was planning to hold an urgent meeting on the situation in Libya.

Nearly 600 migrants and refugees were at the Tajoura detention centre where the attack occurred. Tripoli-based Government of National Accord condemned the attack, calling it a “heinous crime” and accused war criminal Khalifa Haftar for it. Haftar’s Libyan National Army, which has attempted to seize the capital since April, has denied responsibility for the attack.

The United Nations had said that the airstrike killed 44 and injured over 130, but the toll is likely to change. “Coordinates of this detention centre were well-known to both sides of the conflict,” AP quoted UN refugee agency spokesperson Charlie Yaxley as saying. “It was known that there were 600 people living inside. So there can be no excuse for this centre having been hit.”

A spokesperson for Guterres said the United Nations chief condemned the attack, calling for an investigation. “[Guterres] calls for an independent investigation of the circumstances of this incident, to ensure that the perpetrators are brought to justice, noting that the United Nations had provided exact coordinates of the detention centre to the parties,” the statement said.

United Nations envoy to Libya Ghassan Salame had said that the attack “could constitute a war crime, as it killed by surprise innocent people whose dire conditions forced them to be in that shelter,” AP reported.

The European Union along with Turkey and Qatar appealed for an independent investigation. “Those responsible should be held to account,” said European Union diplomatic chief Federica Mogherini, Enlargement Commissioner Johannes Hahn and Migration Commissioner Dimitris Avramopoulos in a statement. France called for a de-escalation and the Arab League urged Haftar and Government of National Accord forces to stop fighting.

Libya became a crossing point for migrants to Europe after dictator Moammar Gadhafi was overthrown in 2011. At least 6,000 migrants from Eritrea, Ethiopia, Somalia, Sudan and other nations are locked in detention facilities in Libya that are run by militias.