Worries over finances of some of the world's governments rippled through financial markets Tuesday, as a series of negative credit-rating actions served as a reminder of the fragility of the global recovery.

Fitch Ratings cut Greece's credit rating a notch to the lowest level in the 16-nation euro zone, raising concerns that Athens could be sparking the biggest fiscal crunch the European monetary union has faced in its 10 years. Moody's Investors Service sliced ratings even more on Dubai government-controlled companies, renewing...