Sepp Blatter resigned as Fifa president on Tuesday, four days after being re-elected to a fifth term.

Blatter, 79, announced the decision at an unexpected news conference in Zurich, six days after the FBI raided a hotel in Zurich and arrested several Fifa officials.

After holding the role for 17 years he was re-elected after his only rival, Jordan’s Prince Ali bin Al Hussein withdrew after losing heavily in the first round of voting.

“I will call an extraordinary congress to elect my successor as soon as possible,” he said. “I am very linked to Fifa and its interests and that is why I have taken this decision.

“What counts most to me is the institution Fifa and football around the world.”

The announcement came as a major surprise to the footballing world, with Blatter adamant he would not step down despite mounting pressure in recent weeks.

Blatter's announcement comes after Fifa has admitted it paid $10million destined for the South Africa World Cup to an account controlled by the disgraced former vice-president Jack Warner. The payment followed a letter from the South African FA to Fifa secretary general Jerome Valcke.

“I had stood again to be elected as I thought it was the best option. The election was closed but the challenges that Fifa are facing have not come to an end. Fifa needs a profound restructuring.

“Although the members of Fifa gave me a new mandate, this mandate does not seem to be supported by everyone in the world.

“I have thoroughly thought about my presidency and the last 40 years in my life. These years were closely related to Fifa. I only want to do the best for Fifa and football.”

Due to existing Fifa rules on the notice periods required for elections and for candidates to present themselves, the election may not take place until at least December.

Domenico Scala, chairman of the Fifa audit and compliance committee addressed the conference after Blatter;

“While the timing will ultimately be up to the executive committee, the timing of election is likely to be between December and March.”

Global Reaction

FAI CEO John Delaney spoke on Tuesday of his ambition that Blatter’s resignation will trigger greater change within Fifa.

“This is good news for world football and not before time,” he said. “These are changes that we had called for and had hoped would come. We believe there is now an opportunity for real change and reform at Fifa.

“It is important that this opportunity to change the culture within Fifa at the highest levels is not passed up.”

Uefa president Michel Platini responded to the news by saying that it was "a difficult decision, a brave decision, and the right decision."

Platini is being touted as a possible candidate in the new presidential election, with Prince Ali saying that he is “at the disposal” of his national organisation to run again.

“I think we need to solve the situation, we need to help football and help the world,” he told CNN news.

Meanwhile the Swiss attorney general have insisted that Blatter is not under investigation by Swiss authorities. Leaving us no closer to the rationale behind Blatter’s sudden change of mind.

“Joseph S Blatter is not under investigation by the OAG. His announced resignation will have no influence on the ongoing criminal proceedings,” they said in a short statement.

• Sepp Blatter's full resignation transcript:

"I have been reflecting deeply about my presidency and about the forty years in which my life has been inextricably bound to FIFA and the great sport of football. I cherish FIFA more than anything and I want to do only what is best for FIFA and for football. I felt compelled to stand for re-election, as I believed that this was the best thing for the organisation. That election is over but FIFA's challenges are not. FIFA needs a profound overhaul.

While I have a mandate from the membership of FIFA, I do not feel that I have a mandate from the entire world of football - the fans, the players, the clubs, the people who live, breathe and love football as much as we all do at FIFA.

Therefore, I have decided to lay down my mandate at an extraordinary elective Congress. I will continue to exercise my functions as FIFA President until that election.

The next ordinary FIFA Congress will take place on 13 May 2016 in Mexico City. This would create unnecessary delay and I will urge the Executive Committee to organise an Extraordinary Congress for the election of my successor at the earliest opportunity. This will need to be done in line with FIFA’s statutes and we must allow enough time for the best candidates to present themselves and to campaign.

Since I shall not be a candidate, and am therefore now free from the constraints that elections inevitably impose, I shall be able to focus on driving far-reaching, fundamental reforms that transcend our previous efforts. For years, we have worked hard to put in place administrative reforms, but it is plain to me that while these must continue, they are not enough.

The Executive Committee includes representatives of confederations over whom we have no control, but for whose actions FIFA is held responsible. We need deep-rooted structural change.

The size of the Executive Committee must be reduced and its members should be elected through the FIFA Congress. The integrity checks for all Executive Committee members must be organised centrally through FIFA and not through the confederations. We need term limits not only for the president but for all members of the Executive Committee.

I have fought for these changes before and, as everyone knows, my efforts have been blocked. This time, I will succeed.

I cannot do this alone. I have asked Domenico Scala to oversee the introduction and implementation of these and other measures. Mr Scala is the Independent Chairman of our Audit and Compliance Committee elected by the FIFA Congress. He is also the Chairman of the ad hoc Electoral Committee and, as such, he will oversee the election of my successor. Mr Scala enjoys the confidence of a wide range of constituents within and outside of FIFA and has all the knowledge and experience necessary to help tackle these major reforms.

It is my deep care for FIFA and its interests, which I hold very dear, that has led me to take this decision. I would like to thank those who have always supported me in a constructive and loyal manner as President of FIFA and who have done so much for the game that we all love. What matters to me more than anything is that when all of this is over, football is the winner."