The National Commission for Human Rights in Libya said late Saturday that the Tunisians were abducted on their way to work at an oil refinery in the western city of Zawiya.
It said the armed group, which it did not name, demanded the release of a Libyan man, also unnamed, detained in Tunisia on drug-related charges.
Tunisia’s Foreign Ministry says the workers were kidnapped on Thursday.
In 2015, an armed militia stormed the Tunisian consulate in Tripoli and took 10 staff members hostage.
Libya slid into chaos after its 2011 uprising that toppled long-time ruler Moammar Gadhafi. The country is currently governed by militia-backed rival authorities in Tripoli and the east.