The six men were held as they were about to board a Turkish Airlines flight to Istanbul from where they had an onward booking to the Qatari capital Doha.
Foreign diplomats worry that Benina airport in the eastern city of Benghazi is being used by extremists to travel to Turkey in order to join anti-government militants in Syria, Reuters reported on Saturday.
Five of the men were definitively of Qatari origin, while the sixth was suspected of being Qatari, the source said.
They had no checked in luggage but carried 180,000 Libyan dinars ($146,000), the officials said.
Libyans do not need a visa for Turkey, which is linked to Benghazi by daily flights. Security is often lax at the small airport.
A UN report revealed in April that weapons are spreading from Libya at an "alarming rate," fueling conflicts in Syria, Mali and elsewhere and boosting the arsenals of militant groups, terrorists and criminals in the region.
Libya’s weapons are sent on ships or by Qatar Emiri Air Force flights to a network of intelligence agencies and Syrian opposition leaders in Turkey. From Turkey, militants distribute the arms.
Extremist militants, some of them aligned with al-Qaeda, have the money to buy the newly arrived stock.
Qatari C-17 cargo aircraft made at least three stops in Libya in 2013 -- including flights from Mitiga airport in Tripoli on Jan. 15 and Feb. 1, and another that departed Benghazi on April 16, according to flight data provided by an aviation official in the region.
Syria has been gripped by deadly violence since 2011. Over 130,000 people have reportedly been killed and millions displaced due to the unrest.
According to reports, the Western powers and their regional allies -- especially Qatar, Saudi Arabia, and Turkey -- support the militants operating inside Syria.
NTJ/HH