Spain's Cadena Ser radio said one of those arrested was former club president Josep Maria Bartomeu.
Police have raided the offices of FC Barcelona, carrying out several arrests just six days ahead of the club's presidential elections, a Catalan regional police spokesperson told AFP.
Spain's Cadena Ser radio said one of those arrested was former club president Josep Maria Bartomeu, who resigned in October, along with CEO Oscar Grau and the club's head of legal services.
But the police refused to confirm names, saying only "arrests are taking place" and adding that the operation was being run by officers from the financial crimes unit.
"We are in the process of carrying out an operation right now with agents of the financial crimes unit," the police spokesperson told AFP.
According to reports in the Spanish media, the operation is linked to last year's investigation into the "BarcaGate" scandal, in which the club denied hiring a company to criticise current and former players on social media to improve the image of the then-president Bartomeu.
BREAKING: Ex-Barcelona president Josep Bartomeu has been arrested today, reports @el_pais 🚨— B/R Football (@brfootball) March 1, 2021
The arrest is reportedly in relation to the "Barcagate" scandal in which the club allegedly hired a social media company to publicly discredit players and staff pic.twitter.com/VU4UzTtM8y
Lionel Messi, Pep Guardiola and Xavi Hernandez were among those allegedly targeted by the campaign. Messi described the controversy as "strange" in an interview with Catalan newspaper Mundo Deportivo.
Cadena Ser also claimed Barca had paid the company, I3 Ventures, an inflated fee and put payments through in smaller, separate amounts to avoid the club's financial controls.
Emili Rousaud, who resigned as Barcelona vice president in March last year, said in an interview with RAC1, "If the auditors tell us the cost of these services is 100,000 euros and we have paid one million, it means someone has had their hand in the till." The club took legal action against him.
Rousaud was among six Barca executives to leave their posts, with a joint letter citing the controversy as a key issue needing to be resolved.
'Juggling everything and plugging gaps'
Bartomeu said the company had been hired only to monitor posts on social media and announced an internal audit by PricewaterhouseCoopers, which cleared the club of financial corruption in July.
"Let one thing be clear," Bartomeu said. "To the question: Have we commissioned the monitoring of social networks? The answer is yes.
"To the question: Have we commissioned to discredit people or institutions through social networks? The answer is no and we will take action against all those who accuse us of that."
Bartomeu resigned in October, avoiding a vote of no confidence triggered after more than 20,000 club members signed a petition against him.
His departure came the same month Barcelona announced losses of $114 million (97m euros) for last season and debts that had more than doubled to $587 million (488m euros).
As well as a series of political blunders, Bartomeu had also overseen a dramatic decline in performances on the pitch and a personal falling-out with Messi, who tried to leave for free last summer.
Messi accused the club of "always juggling everything and plugging gaps" under Bartomeu's leadership.
Bartomeu's successor is due to be elected on Sunday, when club members will choose between the final three candidates, Joan Laporta, Toni Freixa and Victor Font.