Fries, the former chief of communications company Publicis Consultants and a member of the French national audit office, was the only candidate left in the running after Hoog withdrew his bid for a third term.
Hoog's announcement, which he said was due to a lack of government support, came as a surprise just as the board was due to interview the two candidates shortlisted after a CEO search launched in January.
Fries was elected after a third round of voting by the board, which includes representatives of the French press, the government and AFP staff.
Ahead of Thursday's third and final vote, some journalists at AFP's headquarters in Paris staged a two-hour work stoppage to protest what unions feared was a bid to rush in a favoured candidate.
A body representing editorial staff, the SDJ, said it was "surprised and worried by the decision to continue with the selection process, which looks like it is being forced".
The 58-year-old Fries was previously a top executive at French media group Vivendi and advertising firm Havas.
He studied at Berkeley and Harvard in the United States as well as France's elite Ecole Nationale d'Administration (ENA), and led Publicis Consultants until 2016.
AFP is supported financially by the French state, but its editorial independence is guaranteed by an act of parliament.
The agency reported a net loss of 4.8 million euros ($6 million) last year under annual accounts that were validated by the board this week, after losses of 5.5 million euros in 2016.
AFP grew out of Agence Havas, the world's first news agency, founded by Charles Havas in 1835, and is now one of the three biggest news agencies alongside the Associated Press and Reuters.
Today it counts some 2,300 staff including 1,500 journalists, serving media clients around the world as well as in France as the country's national news agency.
Another graduate of ENA, Hoog previously headed the National Audiovisual Institute (Ina) before taking the reins of AFP. He was elected to a second term in 2013.
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