UNITED NATIONS, July 3 (Xinhua) -- UN Secretary-General Antonio Guterres is "outraged" by the overnight airstrikes that hit a detention center east of Tripoli, the capital of Libya, his spokesman said on Wednesday.

The UN chief condemned this "horrendous incident," which killed at least at least 44 migrants and refugees, in the strongest terms, said the spokesman Stephane Dujarric, adding that he expressed deepest condolences to the families of the victims and wishes a quick recovery to those injured.

The secretary-general called 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 center to the parties, said Dujarric.

According to Dujarric, Guterres reminded all parties of their obligations under international humanitarian law to take all feasible precautions to avoid, and in any event to minimize, incidental loss of civilian lives, injury to civilians and damage to civilian objects, and to refrain from directing attacks against civilians.

This incident underscores the urgency to provide all refugees and migrants with safe shelter until their asylum claims can be processed or they can be safely repatriated, he added. "The Secretary-General reiterates his call for an immediate ceasefire in Libya and a return to political dialogue."

Libya has been suffering from escalating violence and political instability since the fall of the late leader Muammar Gaddafi in 2011.