Tunisia mogul, ex-presidential candidate Karoui fined €6mn
"The Tunis court of first instance has sentenced (Karoui) to a fine of 19.5 million dinars," prosecution spokesman Mohsen Dali said.
The case, opened in 2012, concerns "failure to make customs declarations on revenues from export operations", Dali said, without giving details.
Karoui, a business and media mogul whose party Qalb Tounes is part of the current government, is in detention over a separate case of money laundering and tax evasion, stemming from a 2017 investigation.
The 57-year-old was first arrested in August 2019 over that case.
But he came second in the first round of Tunisia's presidential polls, despite being in prison, and was released days before the runoff in October 2019 - won by now-President Kais Saied.
Karoui was released in February on a bail of 10 million dinars, but he did not pay it and was arrested again two weeks later.
His supporters say his human rights have been violated and his case has been used for political ends.
Read also: Tunisian women protest as 'masturbating' MP sworn in
Karoui is the founder of private channel Nessma TV, partly owned by former Italian prime minister Silvio Berlusconi.
His party Qalb Tounes came second in October 2019 parliamentary elections, winning 38 out of 217 seats in parliament.
It has since allied with the Islamist-inspired Ennahdha, the top force in parliament.
Agencies contributed to this report.