Sandler O'Neill & Partners LP, the 24-year-old investment bank that focuses on financial clients, fired about 20 people in units including trading and deal advisory, said people with direct knowledge of the decisions.

Dismissals resulted from a slump in trading and in mergers and acquisitions, said one of the people, who asked to remain anonymous because the reductions were private. The firm will still employ more than 300 people, the person said. Departing executives include Scott Buchta, a managing director and head of mortgage strategy, and Michael Schramm, who traded commercial mortgage-backed securities, the people said.

Economic weakness in the U.S. and Europe's sovereign debt crisis led Wall Street's five biggest banks to post their lowest first-half profit this year since 2008. Citigroup Inc. and Morgan Stanley are among firms shrinking parts of their investment-banking units to reduce costs.

David Franecki, a spokesman for New York-based Sandler O'Neill, declined to comment on the firings. The firm, founded in 1988 with a focus on serving community banks, also has offices in Boston, Chicago, San Francisco, Atlanta and Memphis, Tennessee, according to its website.

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