“The heads are separated from the bodies clad in orange jumpsuits, hands bound behind the back with plastic wire,” said the ministry’s unit for fighting organised crime in the city of Misrata.
It said the bodies of 20 Egyptians and a man of unknown African nationality were unearthed from a mass grave south of the one-time jihadist bastion of Sirte, 450 kilometres (280 miles) east of Tripoli.
Friday’s find came after confessions by Islamic State group jihadist prisoners, it said in a statement, adding that the remains had been transferred to Misrata for forensic examination.
The unit, which answers to the interior ministry of Libya’s internationally recognised Government of National Accord, did not give a date for the possible repatriation of the remains for burial.
IS posted a video on the internet in February 2015 of the beheadings, sparking international condemnation and Egyptian air strikes against jihadist targets in Libya.
Egypt’s foreign ministry said Saturday it had been informed about the discovery of the mass grave.
“The Egyptian embassy has been communicating since Friday with the Libyans with coordination with the Egyptian ministry of defence to secure their return to Egypt,” a spokesman told AFP.