U.S. mergers and acquisitions activity plunged to a 15-year low in August, while global fees for completed deals hit their lowest level since at least 1998, preliminary data showed on Friday.

Thomson Reuters data showed announced U.S. M&A for the month totalled $13 billion, its lowest since February 1994, while global M&A stood at $72 billion, the lowest since February 2003.

Year-to-date, however, European M&A has suffered even more, with total deal value halving to $378.4 billion. U.S. mergers, at $441.5 billion, have fallen 40 percent from a year ago.

European M&A volumes were boosted in August by the takeover tussle that concluded with Volkswagen buying a stake in Porsche and Qatar buying options from Porsche that gave the emirate a 17 percent stake in VW.

The largest U.S. deal was Warner Chilcott's $3.1 billion purchase of Procter & Gamble's prescription drug business.

Fees for completed deals stood at $694 million in August, the lowest since records started in 1998.

Morgan Stanley has overtaken Goldman Sachs as the world's busiest financial adviser by deal volume, working on $439.7 billion of deals in 2009.