The official, on condition of anonymity, told AFP that businessmen Chafik Jarraya, Yassine Chennoufi and Nejib Ben Ismail along with customs officer Ridha Ayari were arrested Tuesday "under the state of emergency" in force in Tunisia since November 2015.
"They are implicated in affairs of corruption and suspected of plotting against state security through incitement and alleged financing of the protest movements in Tataouine and other regions," he said.
A young man, Anouar Sakrafi, died of injuries suffered Monday when he was run over by a national guard vehicle during clashes with security forces at an oil and gas plant in southern Tunisia, the scene of long-running protests over joblessness.
Several dozen people were wounded in the clashes, including around 20 security personnel. But the government said Sakrafi's killing was accidental.
Protesters have been camped outside the El Kamour pumping plant for about a month, blocking trucks from entering, to demand a share of resources and employment in the sector.