Zurich - FIFA on Monday sacked deputy general secretary Markus Kattner for financial 'breaches' involving millions of dollars, according to sources close to an inquiry by the world body.
Kattner's downfall topples another member of ex-president Sepp Blatter's inner circle at football's world body.
Kattner, a German-Swiss national, had been acting general secretary after previous general secretary Jerome Valcke was also dismissed for irregularities.
"Kattner has been dismissed from his position effective immediately," the world body said in a statement.
"FIFA's internal investigation uncovered breaches of his fiduciary responsibilities in connection with his employment contract," it added.
"There was enough to determine there was a breach of his responsabilities and to take action against Mr Kattner," a source close to an internal FIFA investigation said.
"We are talking about significant sums of money, millions of dollars," the source added.
The source said the money came from bonuses under a contract whose terms were kept secret from FIFA audit committees.
The world body indicated that Kattner is the subject of an outside inquiry.
"FIFA will not comment further on any of the details, but will continue its cooperation with the relevant authorities," said the statement.
Swiss prosecutors are already investigating Blatter, who is serving a six year ban imposed by FIFA, and Valcke.
Blatter is under investigation for making a "disloyal" payment of $2 million to ex-UEFA leader Michel Platini, who has also been banned from football activities.
Valcke was sacked and suspended from football activities for 12 years after being linked to the sale of black market World Cup tickets. Swiss police are following up FIFA's investigation against Valcke.
The action is a new blow to FIFA's reputation as it seeks to redeem its scandal-tainted name under new president Gianni Infantino who was elected in February.
Infantino only this month named Fatma Samoura as its new general secretary. Samoura is the body's first woman secretary general and FIFA also wanted her United Nations background to give a sign of football's new direction.
Infantino has repeatedly said he wants to bring a new era of "transparency", "honesty" and "professionalism." But Kattner's dismissal is a new sign that FIFA's past misdeeds have still not all been brought out into the open.
Swiss prosecutors are investigating the awarding of the 2018 and 2022 World Cups to Russia and Qatar.
Court hearings in the United States after the detention of a host of top football officials from South and North America are set to bring new embarrassment.
Acting under US warrants, Swiss police detained seven FIFA officials in a dawn raid on a Zurich hotel on May 27 last year.
US authorities have charged 39 individuals and two companies over more than $200 million in bribes paid for television and marketing deals.