Critics questioning Mayor Giuliani’s stewardship after the World Trade Center attacks marred the presidential candidate’s campaign fund-raising swing through his hometown yesterday that was intended to highlight his national security credentials.

The day got off to a rocky start for Mr. Giuliani, who a day after celebrating his 63rd birthday barnstormed through the city to collect campaign contributions for his White House bid.

During his first stop of the day, in City Island, a woman confronted Mr. Giuliani, accusing him of knowing the twin towers would collapse but allowing rescue workers to remain inside, according to press accounts.

In the evening, reporters expecting to question the Republican at an event in Bay Ridge were instead left covering a street side protest, where the police shut down the block to traffic and cordoned off the anti-Giuliani protesters in a pen across the street.

“We’re trying to peel him back like an onion, layer by layer,” the president of the Uniformed Fire Officers Association, Peter Gorman, said at the rally. “And our message to Rudy is: We’ll be here today on your home turf, in any borough, in any state.”

The crowd included several dozen people, mostly firefighters, who served at the World Trade Center site and family members of those who died after the September 11, 2001, attacks.

The activists have promised to trail Mr. Giuliani as he campaigns to “challenge the premise,” in the words of a civil liberties lawyer working with them, Norman Siegel, “that Rudy Giuliani is America’s hero because of his actions on 9/11 and thereafter.”

“Shame on you!” the crowd shouted as Mr. Giuliani exited a black Cadillac early in the evening. The mayor ignored the protesters across 76th Street as he hurried up the stairs to the Bay Ridge Manor. “Shame on Rudy!”

Protest organizers who hoped to confront Mr. Giuliani on the same side of the street as the catering hall learned shortly before the event that the police had designated the area an emergency “frozen zone,” Mr. Siegel said.

“This is perhaps an indication of what America could be in the future if Rudy Giuliani becomes president,” Mr. Siegel said, shaking the metal police barricades. “And these barriers will become the symbol of a Giuliani presidency.”

The Giuliani campaign did not immediately return a phone call seeking comment last night.

Although the shouting protesters drew the attention of neighbors and the press, they made considerably less of an impact inside the Bay Ridge Manor, several of the donors said after the fund-raiser.

“The dinky little demonstration?” a 73-year-old retired bank officer who paid $250 to attend the fund-raiser, Louis Mita, said. Wearing a vintage Rudy for Mayor lapel pin, Mr. Mita said, “They’re wasting their time.”