"That would be letting them win, the terrorists and lunatics," she said.
Marathon organizers plan to donate money to a Boston fund set up to help victims. They said they did not consider canceling the event, which is a highlight of the sporting calendar.
In a smaller event in Germany, some 15,000 runners were participating Sunday in the Hamburg Marathon. They wore armbands with the slogan "Run for Boston" as a mark of respect for the bombing victims.
Hamburg's top security official, Michael Neumann, has said that security "is adapted to the situation," without giving further details.
There was a brief security scare at a Hamburg subway station after the race started when a suspicious object was found. The station, which isn't on the race route, was closed while officials checked the object — which turned out to be an empty cardboard box, news agency dpa reported.
There was no disruption to the marathon. Hamburg organizers have said that they know of only eight people who pulled out because of the Boston bombings.