Sepp Blatter is to resign as president of world football's governing body Fifa as reports emerge he is under investigation in the United States.

The Swiss was re-elected last week, despite seven top Fifa officials being arrested in a massive corruption probe.

Announcing his shock exit, the 79-year-old Blatter, who has been in power for 17 years, said: "My mandate does not appear to be supported by everybody."

He plans to carry on his duties until a replacement can be elected.

Fifa has been dogged by corruption allegations for years now but it was rocked to its core last week by the arrests of seven Fifa officials on charges of racketeering, wire fraud and money laundering.

The charges are part of a US prosecution that indicted a total of 14 people from around the globe.

Further allegations emerged on Tuesday that increased the pressure.

Reports also claimed Fifa general secretary Jerome Valcke was responsible for an alleged payment of a $10m (£6m) bribe in relation to South Africa's bid to host the 2010 World Cup.

The 54-year-old Frenchman denies any wrongdoing.

A separate criminal investigation by Swiss authorities into how the 2018 and 2022 World Cups were allocated is also under way.