Porto communications director Francisco J. Marques has accused the Portuguese champions Benfica of resorting to sorcery to win the past two seasons.
Marques told local TV channel Porto that he saw emails that Benfica president Luis Filipe Vieira and Dr. Armando Nhaga, the national Police Commissioner of Guinea-Bissau, exchanged earlier this year regarding agreements for witchcraft services.
Marques told reporters: "In 2015-16, Benfica spent €75,000 (£65,945) to fix the Championship [using sorcery]."
The Porto communications chief claimed that Nhaga warned Benfica that their attempts to win a fourth straight league title could be in jeopardy due to "sabotage" if the club did not increase their payments for using their services with respect to the 2015-16 campaign.
Vieira was reportedly not aware of the deal that was in place between a former ex-board member of the club, Rui Gomes da Silva, and Nhaga for that season. There was an agreement that also included the possibility of renewal.
However, Gomes da Silva did not maintain his place on the board.
Nevertheless, he alleged that Vieira was willing to consider an agreement.
The Porto chief claimed he saw an email that Nhaga sent to Vieira which said: "Regarding the 2016-17 campaign, which starts on Aug. 7 with the [Portuguese] Supercup, it could be a close fight for the [league] title, in which Benfica can make history.
"This entails the urgent need to reach a mutual agreement to provide services for the parties."
Nhaga then reportedly sent an itemised list of fees for his services for the season -- including €100,000 (£88,000) to win the league title and a fee of €30,000 (£26,398) for every Champions League knockout game.
However, Benfica lost 4-0 at Borussia Dortmund on March 8 to be eliminated from the Champions League round of 16. Marques alleged that after the loss, Vieira sent an e-mail to Nhaga asking "what happened?"
Nhaga replied that he was not "in Guinea at the time and that whoever was dealing with it [alleged sorcery] did not do it at the right time," but reportedly said: "However, now we are going to concentrate on what is essential, which is the league title and the Portuguese Cup. I thank you for your understanding and this will not happen again."
Marques said he was disgusted by the revelations.
"We are talking about witchcraft," he said. "Hundreds of thousands of euros were spent on that.
"I don't know what to make of this.
"This calls into question the coach, the players, but also [club executives] Paulo Goncalves and Pedro Guerra.
"There are people that in order to win, anything goes."
Benfica won a record fourth straight Portuguese league title in May with one game to spare, with Porto finishing runners-up, six points adrift.
The Lisbon-based club also lifted the Portuguese Cup after beating Vitoria Guimaraes 2-1.