European financial-services firm AXA ( AXA) agreed to buy the insurance provider Winterthur from Credit Suisse Group ( CSR) for $9.9 billion.

Winterthur is active in 17 countries and serves 13 million clients worldwide. The firm is one of the top 10 composite insurers in Europe with a leading position in Switzerland and a strong presence in Germany, Spain, Belgium, the Netherlands, Luxembourg and the U.K.

Paris-based AXA said in a press release Wednesday that life and savings accounts for 62% of Winterthur's insurance revenue, while property and casualty makes up the other 38%.

"This transaction is a unique opportunity to reinforce our leading position in our core European market and to increase our presence in high growth markets, notably in Central and Eastern Europe and in Asia," said Henri de Castries, AXA's chief executive, in a statement.

AXA's American depositary shares fell 52 cents to $29.79. Credit Suisse was up $1.56 to $51.63.