South Korea's FIFA sponsor Hyundai Motor on Monday called for "prompt and transparent" reforms of world football's governing body without commenting directly on its scandal-tainted chief.

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"The current reforms by FIFA should be conducted in a prompt and transparent manner," the auto group said in a brief statement.

Last week major sponsors including Coca-Cola, McDonald's, Visa and Budweiser called for Sepp Blatter's immediate resignation, after Swiss prosecutors opened a criminal investigation against the 79-year-old over mismanagement. 

Blatter remained defiant, saying his departure would not best serve FIFA's interests and that he did not plan to resign before February, when a special election has been called to choose his replacement. 

Exposure of the rot within FIFA had already sparked widespread calls for immediate change, but the rare display of unity from four major sponsors marked the first time key financial backers had explicitly demanded Blatter's resignation.

The crisis of world football began in May, when nine FIFA officials and five sports marketing executives were charged by the US Justice Department over bribery worth more than $150 million dating back to 1991.

Blatter was re-elected as FIFA's president days later, but on June 2, made the shock announcement that he was prepared to go — on a timeline that he subsequently laid out.

His former right-hand man, secretary general Jerome Valcke, was suspended over allegations that he was aware of a black market ticket scheme surrounding the 2014 World Cup. Valcke denied the claims.