A statement said the six were arrested yesterday in the Monastir region in the east of the North African country.
The suspects, aged between 19 and 51, admitted being in contact with Islamic State group jihadists in neighbouring Libya and recruiting Tunisians to fight in Syria, it said.
The six also said that they themselves had undergone clandestine "military" training "with the aim of joining jihadist groups abroad", it added.
According to the United Nations, more than 5,500 Tunisians, mostly aged between 18 and 35, have joined jihadist organisations in conflict-riddled Syria, Iraq, Libya, Yemen and Mali.
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Last month, parliament voted to set up a commission of inquiry into "jihadist channels" and their recruitment.
Since the 2011 Tunisian revolution that sparked the Arab Spring, the country has experienced a rise in jihadist activity that has killed more than 100 soldiers and police, some 20 civilians and also 59 foreign tourists.
Authorities have cracked down on extremists since a November 2015 attack in central Tunis killed 12 members of the presidential guard and a March 2016 jihadist attack on the town of Ben Guerdane near the border with Libya.