New York, New York - Zohran Mamdani has been publicly sworn in by Senator Bernie Sanders as New York City's new mayor in an inauguration ceremony on the steps of City Hall.

"My fellow New Yorkers, today begins a new era," Mamdani said. "I stand before you moved by the privilege of taking this sacred oath, humbled by the faith that you have placed in me, and honored to serve as either your 111th or 112th mayor of New York City."

"Over the years to come, my administration [...] will deliver an agenda of safety, affordability, and abundance, where government looks and lives like the people it represents, never flinches in the fight against corporate greed, and refuses to cower before challenges that others have deemed too complicated," Mamdani vowed.

As NYC's first Muslim mayor, Mamdani was also the city's first to take his oath of office with his hand on a Quran, held by his wife Rama Duwaji.

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Before administering the oath, Sanders thanked New Yorkers for voting for Mamdani and volunteering for his mayoral campaign.

"In the process, you took on the Democratic establishment, the Republican establishment, the president of the United States, and some enormously wealthy oligarchs, and you defeated them in the biggest political upset in modern American history," Sanders said.

"When working people stand together, when we don't let them divide us up, there is nothing we cannot accomplish!" he added.

Representative Alexandria Ocasio-Cortez delivered welcoming remarks in Thursday's public ceremony, which also included the swearing in of New York City Comptroller Mark Levine and Public Advocate Jumaane Williams.

"In Zohran Mamdani, we have chosen a mayor who is relentlessly dedicated to making life not just possible but aspirational for working people," AOC said.

Around 4,000 ticketed guests were expected to attend the event outside City Hall. Mamdani's team also organized a block party it said would allow tens of thousands of people to watch the ceremony along Broadway.

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Several hours prior, Mamdani took the oath of office at midnight in a private ceremony at a decommissioned subway stop. He was officially sworn in by New York Attorney General Letitia James.

"I was elected as a democratic socialist, and I will govern as a democratic socialist. I will not abandon my principles for fear of being deemed radical," the new mayor told the crowd on Thursday afternoon.

"The work continues. The work endures. The work, my friends, has only just begun."