Foreign Ministry spokesman Badr Abdel-Atti said men in military uniform took the 70 from their homes in Tripoli. Abdel-Atti said the Egyptians were taken to a police facility in Tripoli.
Details were sketchy and it was not known who the armed men were. Libyan authorities did not immediately comment on the incident.
Abdel-Atti said Egypt's foreign minister is contacting his Libyan counterpart to get the Egyptians released.
Since the 2011 civil war, Libya has struggled with a weak central government and unruly militias, most of which stem from rebel groups that ousted dictator Muammar Gaddafi.