Tunisian police arrested presidential candidate Nabil Karoui on Friday after a court ordered his detention, the Interior Ministry said, in a case involving charges of money laundering but which Karoui's party said was a politically motivated attempt to exclude him from the election race.

Karoui's own Nessma TV channel reported that the candidate had been arrested as he traveled to Tunis, and broadcast a video showing the police detaining him in his car.

The 56-year-old media magnate is one of the main candidates contesting the September 15 election following the death of President Beji Caid Essebsi.

"The indictment chamber charged in the cases of financial corruption decided today to issue two prison deposit cards against Nabil Karoui and his brother Ghazi Karoui," Saber Horchani, the spokesman for the appeal court, told state news agency TAP.

A judge ordered the detention of Karoui to face charges of tax evasion and money laundering, Mosaique FM radio reported.

A judge decided in July this year to bar Karoui from traveling abroad after weeks of investigation on suspicion of money laundering.

"The police arrested Karoui while we were on our way back from the city of Beja to Tunis," said Osama Khelifi, a political adviser to the candidate. "They kidnapped the most prominent candidate in the presidential election so that (Prime Minister Youssef) Chahed can win the election in an open way," he added.

Samira Chaouachi, spokeswoman of Karoui's Heart of Tunisia Party, said it was "a political arrest aimed at keeping Karoui out of the presidential race."

Chahed and Karoui are among 26 candidates running for the presidency following Essebsi's death last month at age 92. Essebsi was the first head of state to be democratically elected in Tunisia following the popular uprising of 2011.

Other candidates include former president Moncef Marzouki and Abd El Fatteh Mourou, vice president of the moderate Islamist Ennahda party.

Tunisia's president controls foreign and defense policy, governing alongside a prime minister chosen by Parliament who has authority over domestic affairs.

Karoui founded the Khalil Tounes Foundation in 2017 to fight poverty, the main theme in his campaign.

In April, police stormed the offices of Nesma channel, which promotes Karoui's candidacy and career, and took it off the air over accusations that it had breached broadcasting rules. Nesma said it was a move to stop it criticizing the government.

(Cover image: Nabil Karoui, businessman and owner of the private channel Nessma arrives at the Financial and Economic Judiciary pole in Tunis, Tunisia, July 12, 2019. /VCG Photo)