The Swiss Attorney General's office has announced that it has opened criminal proceedings against FIFA president Sepp Blatter on suspicion of criminal mismanagement and a separate claim of misappropriation.

UEFA chief Michel Platini, a frontrunner to succeed Blatter in the top job in world football when the 79-year-old steps down, is also implicated in the allegations as it is claimed that he received a "disloyal" payment from Blatter in 2011.

In a statement, the OAG confirmed that it is focusing on this as one of two allegedly illicit transactions, the other being a deal with then-Caribbean Football Union chief Jack Warner in 2005, thought to be related to TV rights.

The statement reads: "On the one hand, the OAG suspects that on September 12, 2005 Mr Joseph Blatter has signed a contract with the Caribbean Football Union (with Jack Warner as the President at this time); this contract was unfavourable for FIFA.

"On the other hand, there is as suspicion that, in the implementation of this agreement, Joseph Blatter also violated his fiduciary duties and acted against the interest of FIFA.

"Additionally, Mr Joseph Blatter is suspected of a disloyal payment of CHF 2 Mio. [two million Swiss francs] to Michel Platini, President of Union of European Football Associations (UEFA), at the expense of FIFA, which was allegedly made for work performed between January 1999 and June 2002; this payment was executed in February 2011."

The Office goes on to say that its own representatives interrogated Blatter on Friday following a meeting of the FIFA Executive Committee, with Platini heard "as a person asked to provide information".

The OAG has also conducted a house search at FIFA Headquarters with the support of the Federal Criminal Police, and the office of the FIFA President has been searched and data seized.

In its own official statement, FIFA replied: "Since May 27, 2015, FIFA has been cooperating with the Office of the Swiss Attorney General and has complied with all requests for documents, data and other information. We will continue this level of cooperation throughout the investigation.

"Today, at the home of FIFA, representatives from the Office of the Swiss Attorney General conducted interviews and gathered documents pursuant to its investigation. FIFA facilitated these interviews as part of our ongoing cooperation.

"We will have no further comment on the matter as it is an active investigation."

Blatter has been president of FIFA since 1998.