Zohran Mamdani sworn in as mayor of New York City

Zohran Mamdani was sworn in as mayor of New York City early on Thursday, becoming the first Muslim and the youngest in generations to take the oath of office in the largest city in the United States.

The 34-year-old leftist politician, placing his hand on a Koran, was sworn in shortly after midnight by New York State Attorney General Letitia James in a small ceremony at the historic Old City Hall subway station.

Mamdani, who was accompanied by his wife Rama Duwaji, said the post was "the honour and the privilege of a lifetime."

In his first words as mayor, Mamdani also announced the appointment of a new transport commissioner.

Tens of thousands of New Yorkers defied the freezing winter weather to attend a second, public swearing-in ceremony later on Thursday on the steps of New York City Hall, with left-wing Senator Bernie Sanders administering the oath of office.

New York Congresswoman Alexandria Ocasio-Cortez hailed Mamdani for his commitment to the working class, saying his tenure "marks new era for New York City."

The people of New York "have chosen historic, ambitions leadership in response to untenable and unprecedented times," she said, eliciting smiles from Mamdani sitting on the podium.

"We have chosen prosperity for the many over spoils for the few."

Mamdani won the election in early November, securing a four-year term as mayor. He brands himself as a democratic socialist and campaigned on an affordability platform, promising free childcare, free buses and rent control for millions of households, funded by higher corporate taxes and taxes on the wealthy.

His office said the choice of the decommissioned Old City Hall station for the ceremony was intended to underscore Mamdani's connection to the working class.

Born in Uganda in 1991, Mamdani moved to New York at the age of 7, and was granted US citizenship in 2018.

Beginning his political life as a grassroots activist, before winning an Assembly seat for Queens in 2020.

Mamdani is the youngest person to hold the position of New York mayor since the 19th century.

US President Donald Trump repeatedly attacked Mamdani in the run-up to the vote and threatened to withhold federal funds from New York if the Democrat won.

Mamdani himself has been a vocal critic of the president, whose administration has taken drastic action against people who entered the country illegally.

However, in their first meeting at the White House following Mamdani's triumph, the two struck a surprisingly positive note.

Taking office at the turn of the year is a long-standing tradition in New York. Mamdani's predecessor, Eric Adams, took his first oath of office in Times Square, and the mayor before him, Bill de Blasio, took his at his home in Brooklyn.