World stocks fell Friday after credit downgrades slapped on Spanish banks unnerved investors already worried about the stability of the 17-country euro currency union.

Political turmoil in Greece has increased the likelihood that it could leave the 17-country monetary union, a move that could have ripple effects throughout Europe and the world’s financial markets.

Markets were jolted by Moody’s downgrade Thursday of 16 Spanish banks, said Jackson Wong, vice president at Tanrich Securities in Hong Kong.

In currencies, the euro fell to $1.2686 from $1.2714 late Thursday in New York. The dollar rose slightly to 79.30 yen from 79.28 yen.