Libya's internationally recognized government and its forces have carried out widespread arbitrary detentions and torture in prisons in the east of the country, Human Rights Watch said on Wednesday.
Four years after the fall of Muammar Gaddafi, Libya is in turmoil with two rival governments -- the recognised one based in the east and a self-declared administration controlling Tripoli -- fighting on several fronts.
In a report released on Wednesday, the New York-based group said in January and April 2015 it gained rare access to detention facilities in al-Bayda and Benghazi controlled by the Libya Army and Justice and Interior ministries, and interviewed 73 detainees individually without guards present.
"Many detainees said that interrogators had forced them under torture to 'confess' to serious crimes," the report said.
The report said detainees described other abuses, including lack of due process, scarce medical care, lack of notification of families about their detention, and poor conditions.
The wardens of Kawaifiya prison in Benghazi and Ghernada in al-Bayda rejected all the allegations.
"The allegations of torture and ill-treament that have been mentioned in a report by HRW were completely untrue," they said in a statement.
"We, wardens of Kawaifiya and Gheranda prisons, invite the media to visit the prisons to meet the detainees and write reports and assess the situation."
According to the report, detainees said they had been beaten with plastic pipe, electrical cable, chains or sticks.
Detainees also reported electric shocks, prolonged suspension, insertion of objects into body cavities, solitary confinement and denial of food and hygiene facilities.
Human Rights Watch director of Middle East and North Africa Sarah Leah Whitson said: "Government ministers, military commanders and prison directors should immediately declare a no-tolerance policy against torture and hold anyone who abuses detainees to account."
Ministers of interior and justice for the official government were not available for immediate comments.
Rebel forces who fought side-by-side in 2011 to end the autocratic rule of Mummar Gaddafi have since become rival factions in a scramble for power in the North African OPEC member. The United Nations has been organising peace talks.