Swiss prosecutors said Thursday that they had filed an appeal against the acquittal of former football chiefs Sepp Blatter and Michel Platini over a suspected fraudulent payment.

Blatter and Platini, once the chiefs of world and European football respectively, were cleared on July 8 by the Federal Criminal Court in a trial following a mammoth investigation that began in 2015.

The Office of the Attorney General of Switzerland (OAG) told AFP that it had filed the appeal before the deadline was reached Wednesday night, confirming a report in L'Equipe.

Switzerland's top prosecutor "has applied for the full annulment of the first-instance judgement," a spokeswoman for the Office of the Attorney General wrote in an email.

The prosecutors reportedly had 20 days to make their intentions clear after the reception of the full verdict from the Federal Criminal Court, based in the southern city of Bellinzona, on September 29.

Former FIFA president Blatter, 86, and Platini, 67, were cleared of the allegations that shook world football and torpedoed their time at the top.

The Federal Criminal Court rejected the prosecution's request for a suspended prison sentence of a year and eight months.

The trial revolved around payment for Platini's work as an adviser to Blatter between 1998 and 2002.

Platini was accused of having submitted to FIFA in 2011 an allegedly fictitious invoice for a claimed debt still outstanding for his advisory work.

They signed a contract in 1999 for an annual remuneration of 300,000 Swiss francs, which was paid in full by FIFA.

But the pair were tried over a two million Swiss franc ($2.06 million) payment in 2011 to Platini, who was then in charge of European football's governing body UEFA.

Blatter told the court the pair had actually struck a "gentleman's agreement" for Platini to be paid a million Swiss francs a year.

Both were accused of fraud and forgery of a document. Blatter was accused of misappropriation and criminal mismanagement, while Platini was accused of participating in those offences.

The court concluded that fraud was "not established with a likelihood bordering on certainty", and therefore applied the general principle of criminal law according to which "the doubt must benefit the accused".