NEW ORLEANS —Former New Orleans Mayor Ray Nagin stood before a federal magistrate judge Wednesday afternoon and in a stern tone pleaded not guilty to nearly two dozen federal charges, including conspiracy, bribery, wire fraud and filing false income tax returns while serving as leader of this city.

U.S. Magistrate Judge Sally Shushan set Nagin’s bail at $100,000 and set April 29 as a preliminary trial date. The case is assigned to U.S. District Judge Ginger Berrigan.

A grand jury last month handed up a 21-count indictment against Nagin, who prosecutors allege accepted more than $200,000 in bribes and other goods — including granite and free trips — from contractors in exchange for helping them to secure city work that was worth millions of dollars.

Nagin surrendered his passport Wednesday and was prohibited from traveling anywhere outside of Louisiana or Texas. Nagin now lives in Frisco, Texas, a Dallas suburb.

Asked minutes before the hearing if he had anything to say about the charges he faces, Nagin said he didn’t.

“No, man. I can’t make any comments,’’ Nagin said as he walked from his attorney’s office on St. Charles Avenue to the nearby Hale Boggs Federal Courthouse. He responded to no other questions from a gaggle of reporters who crowded him as he entered and left the courthouse.

Nagin’s attorney, Robert Jenkins, also said little to the media scrum.

“We don’t have any comments. We’re preparing for trial. That’s all I can tell you,” Jenkins said as he and Nagin left court.

Nagin has consistently maintained his innocence and said he would fight the charges.

The city’s former chief executive appeared calm and relaxed as he entered the courthouse. He even shared a few laughs with Jenkins in the courtroom before the proceeding began. He was more stoic as he walked back to Jenkins’ office, staring straight ahead and saying nothing.

It was the first court appearance for Nagin, 56, in a legal saga that has seen several of his former associates taken down on federal charges. Wednesday was also the first public appearance here for Nagin since his indictment.

Voters elected Nagin in 2002 on promises of rooting out perceived corruption at City Hall. He led the city through Hurricane Katrina and was returned to office in 2006. He left office in May 2010, when term limits prevented him from seeking the city’s top office again.

Nagin’s post-Katrina tenure appears to be when his reputation as an anti-corruption mayor began to crumble.

Prosecutors allege Nagin accepted more than $160,000 in bribes and loads of granite for a family business in exchange for issuing millions in post-Katrina city contract work to businessman Frank Fradella, who pleaded guilty in June to conspiracy to commit bribery.

Prosecutors also charged that Nagin accepted at least $60,000 in payoffs from businessman Rodney Williams and then secured several city contracts for him. Williams, who was president of Three Fold Consultants LLC, pleaded guilty late last year to a charge of conspiracy.

Additionally, the indictment alleges that Nagin received free private jet and limousine services to New York from someone identified only as “Businessman A.” That person owned a movie theater in eastern New Orleans between August 2002 and May 2010, according to the indictment. Prosecutors claim that in May 2006, Nagin agreed to waive unpaid tax penalties on a delinquent tax bill the businessman owed the city.

Nagin also is accused of accepting free travel and vacation expenses for trips to Hawaii, Chicago, Las Vegas and Jamaica from several city contractors while in office.

The alleged bribery plot isn’t limited to Nagin’s time as mayor. Prosecutors claim he accepted nine payoffs from Fradella totaling $112,250 once he left office.

That same year, Greg Meffert, a former technology official in Nagin’s administration, pleaded guilty to charges he took bribes and kickbacks in exchange for steering city contracts to businessman Mark St. Pierre. Anthony Jones, who served as the city’s chief technology officer in Nagin’s administration, also pleaded guilty to taking payoffs.

Meffert cooperated with the government in its case against St. Pierre, who was convicted in May 2011 of charges that include conspiracy, bribery and money laundering. According to the indictment, Nagin accepted bribes from St. Pierre, including free travel and lodging, cellphone service for relatives and campaign funding.

Aaron Bennett, a businessman awaiting sentencing in a separate bribery case, has said he introduced Nagin to Fradella specifically to help the mayor get Home Depot granite installation work for Stone Age LLC, a business that he founded with his sons, Jeremy and Jarin. Fradella’s company received more than $4 million in city contracts for repair work at Louis Armstrong New Orleans International Airport and in the French Quarter after Katrina, according to the indictment.

“Family Member 1” and “Family Member 2” are alleged coconspirators. Those two people appear to be Jeremy and Jarin Nagin, who last fall appeared before a grand jury in response to a subpoena. Nagin’s sons have not been charged with any crimes.

Nagin was an executive with Cox Cable before he was elected to his first term as mayor. Buoyed by strong support from white voters, he cast himself as a reform-minded progressive who was not bound by party affiliations as he snubbed fellow Democrats.

Strong support from black voters helped Nagin win re-election in 2006, despite widespread criticism of his post-Katrina leadership and the pace of the city’ recovery.

However, the glacial pace of rebuilding, a surge in violent crime and the budding City Hall corruption investigation chipped away at Nagin’s popularity during his second term.

Nagin, who sold his Gentilly home before he moved to Texas, has largely steered clear of the political arena since he left office. On a Twitter account he often uses, he describes his occupations as author, public speaker and “green energy entrepreneur.”