The bodies of De Salis and a New Zealand woman described as a close friend were found on a beach near an oil and gas facility Thursday.
In a statement issued by the Foreign Office, De Salis' family said "Mark enjoyed his work in Tripoli and liked the Libyan people."
Britain has called on the Libyan government to investigate the "murder" of De Salis and his friend, saying British diplomats in Tripoli were "liaising closely" with Libyan authorities.
"The exact circumstance of their deaths is not yet clear and will be subject to an investigation by the Libyan authorities," the New Zealand Foreign Ministry said in a statement.
A U.S. teacher was shot to death last month while on a run in Benghazi. Four U.S. military personnel were briefly detained a week ago not far from where De Salis and his friend were killed.