Of the nearly 3,000 people who were murdered when hijacked planes struck and destroyed New York's World Trade Center, over 1,200 were employees of financial services firms.

The New York Mercantile Exchange Inc. observed moments of silence at 8:46 a.m. and 9:03 a.m., the times at which the two towers of the World Trade Center were struck, and on 9:59 a.m. and 10:29 a.m., when the towers collapsed.

It also held a memorial service at 2:45 p.m. to pay tribute to the 32 traders who perished that day.

Guests at the New York Stock Exchange opening bell ceremony included President Carmine Calzonetti and Executive Director Terry Sears of Tuesday's Children, as well as family members of 9/11 victims.

Tuesday's Children is a platform of programs, services and resources that have assisted family members affected in the attacks.

The American Stock Exchange invited New York Firefighters Chris Tighe and Jimmy Andruzzi from Ladder Company 3 to ring the opening bell.

The Nasdaq Stock Market Inc. aired a live feed of the official New York City memorial service and also held a moment of silence at 10:29 a.m.

Marsh & McLennan Cos. Inc., a New York-based insurance company, which lost 295 employees that day, held a private remembrance ceremony at its New York headquarters where its 9/11 Memorial is located.

The event included remarks by chief executive Michael G. Cherkasky, a moment of silence at 8:46 a.m. and a musical tribute by the Marsh Singers.

Aon Corp., a Chicago-based insurance company that lost 175 employees in the attacks, sent a letter to the company's 43,000 staffers marking the anniversary of the attacks. and observed a moment of silence at 10:29 a.m.

Keefe, Bruyette & Woods Inc., a New York-based broker-dealer and investment bank, which lost 67 members that day, will have a company gathering in front of its memorial plaque at the Central Park Zoo this evening, said a company spokesman.