The investigators commissioned by the UN Human Rights Council also faulted the European Union for sending support to Libyan forces that they say contributed to crimes against migrants and Libyans.
Their findings come in an extensive new report, based on interviews with hundreds of people, including migrants and witnesses, that wraps up a fact-finding mission created nearly three years ago to probe rights violations and abuses in the North African country.
The investigators said they collected at least 2,800 items of information documenting numerous cases of arbitrary detention, murder, torture, rape, enslavement, sexual slavery, extrajudicial killings and enforced disappearances that confirmed their widespread practice in Libya.
“It is clear that there was a pattern of violation of human rights and international humanitarian law. Particularly in places of detention as well as in relation to migrants,” investigator Chaloka Beyani told Al Jazeera.
Libya has in recent years emerged as the dominant transit point for refugees and migrants from Africa and the Middle East who are seeking to reach Europe. Human rights groups and activists have long decried the horrible conditions these people are facing.
During the probe into alleged human trafficking and smuggling, the investigators found “there are reasonable grounds to believe that migrants across Libya are victims of crimes against humanity and that acts of murder, enforced disappearance, torture, enslavement, sexual violence, rape and other inhumane acts are committed in connection with their arbitrary detention”, the report said.
It specifically cited the Libyan coastguard, which has been supported by the EU over the years.
“The support given by the EU to the Libyan coastguard in terms of pull-backs, pushbacks, (and) interceptions led to violations of certain human rights,” said Beyani. “You can’t push back people to areas that are unsafe, and the Libyan waters are unsafe for the embarkation of migrants.”
The investigators also expressed concern about the deprivation of liberty of Libyans and migrants throughout the country, in what they said could also amount to crimes against humanity.
They found numerous cases of “arbitrary detention, murder, torture, rape, enslavement, sexual slavery, extrajudicial killing and enforced disappearance” throughout Libya.
People held in detention were regularly subjected to “torture, solitary confinement, held incommunicado, and denied adequate access to water, food, toilets, sanitation, light, exercise, medical care, legal counsel, and communication with family members”, the investigators said.
But they said nearly all the survivors they interviewed did not lodge official complaints out of fear of reprisals, arrest, extortion and a lack of confidence in the justice system.
The three-member panel said there was a broad effort by the authorities in Libya to repress dissent by civil society.
The investigation found that Libyan authorities, notably the security sectors, were curtailing the rights to assembly, association, expression, and belief in order to ensure obedience, entrench self-serving values and norms, and punish criticism against authorities and their leadership.
Libya was plunged into turmoil after a NATO-backed uprising in 2011 toppled longtime ruler Muammar Gaddafi, who was later killed, and left the country divided between rival governments in the east and west.