|Hammam has accused Blatter of not acting in accordance with FIFA's rules on reporting apparent corruption [EPA]
World football's governing body FIFA has opened ethics proceedings against its own president Sepp Blatter, following a request from presidential election rival Mohamed bin Hammam.
The announcement comes just three days before the election for the biggest job in world football and is the latest in a series of corruption charges levelled at FIFA officials.
"FIFA Ethics Committee today opened a procedure against the FIFA President in compliance with art. 16 of the FIFA Code of Ethics," the body said in a statement on Friday.
"Joseph S. Blatter has been invited to take position by 28 May 2011 ... and to attend a hearing by the FIFA Ethics Committee at the Home of FIFA (Zurich) on 29 May 2011."
Bin Hammam, a contender for the FIFA presidency who has also been accused of being involved a bribery scandal, earlier urged FIFA to investigate his rival.
In a statement issued shortly after a scheduled FIFA finance meeting in Zurich on Thursday, Bin Hammam accused Blatter of violating FIFA's behaviour code.
Bin Hammam, the Qatari head of the Asian Football Confederation president, along with Jack Warner, a FIFA vice-president, stands accused of offering bribes to 25 Caribbean football leaders during a May 10-11 campaign trip to Warner's native Trinidad.
He has rejected the allegations, and now says that Blatter broke FIFA's ethical code by not reporting an apparent corruption attempt.
"The accusations also contain statements according to which Mr. Blatter, the incumbent FIFA president, was informed of, but did not oppose, payments allegedly made to members of the Caribbean Football Union," Bin Hammam's statement read.
Bin Hammam insists that the scandal is part of a "plan to damage" his candidacy and has questioned the timing of the allegations.
"I cannot comment on the proceedings that have been opened against me. The facts will speak for themselves."
In response to FIFA's probe, Blatter released a statement saying: "I cannot comment on the proceedings that have been opened against me. The facts will speak for themselves.''
Earlier, in a regular campaign column on a football website, Blatter spoke of Bin Hammam's "public humiliation", but denied that he was conspiring to remove his challenger from the ballot.
He wrote that he was "shocked" by the corruption allegations against Bin Hammam, which shed "a very bad light on FIFA yet again".
"It gives me no pleasure to see him suffer public disgrace before an investigation would even have started," Blatter said in a column for Inside World Football. "To now assume that ... this entire matter was somehow masterminded by me is ludicrous and completely reprehensible."
The two election rivals met briefly on Thursday in FIFA's main committee forum. A hearing into Bin Hammam's case is due in Zurich on Sunday.
The presidential poll of up to 208 football nations is scheduled for next Wednesday, but the ethics panel could effectively hand Blatter victory if it suspends the AFC president from all football duty.
It could choose to do so if it rules that wrongdoing has been proven, or if it requests more time to study evidence compiled by a federal prosecutor for the North, Central, American and Caribbean (CONCACAF) football regional body. The latter would result in Bin Hammam being provisionally barred.
Nine of FIFA's 24-man executive committee are currently under investigation, and the latest spate of allegations has led major sponsor Adidas, a top-tier backer of the body since the 1970s, to lament the "negative tenor" of FIFA's debate.
With both presidential candidates now under investigation, it is unclear whether next Wednesday's election will go ahead.