DUBAI, June 3 (Reuters) - Qatar's stock index .QSI tumbled 2.8 percent to a six-week low in early trade on Wednesday after Sepp Blatter unexpectedly resigned as president of soccer's world governing body FIFA.

Doha was chosen to host the FIFA 2022 World Cup in a 2010 vote. But that decision has been dogged by controversy and Blatter's decision to quit, just days after he was elected as FIFA president for a fifth term, appeared to increase investor fears that Qatar could be stripped of its hosting rights.

It is not yet clear whether Qatar faces a serious risk of losing the rights; it has denied any wrongdoing in the bidding process, and appears set to fight any attempt to take away the Cup. Losing it would have very little impact on the super-wealthy economy.

But Qatari retail investors have reacted emotionally in the past year to any suggestion that the World Cup might be lost.

(Reporting by Matt Smith; Editing by Andrew Torchia) ((Hadeel.AlSayegh@thomsonreuters.com; +971566883310;))

Keywords: QATAR STOCKS/FIFA