New York commemorated the 25th anniversary of the devastating attacks of September 11, 2001 on Friday with a ceremony marred by controversy over President Donald Trump’s absence, and right-wing outrage over the attendance of the city’s first Muslim mayor.

In an unusual move, Trump paid his respects at the Pentagon, rather than joining the event in New York, where hijacked planes destroyed the World Trade Centre and killed most of the 2,977 total victims on that world-altering day.

Vice President JD Vance and Trump’s four living predecessors — Republican George W. Bush, who was in office during the attacks, and Democrats Joe Biden, Barack Obama and Bill Clinton — were gathering at the Ground Zero site in lower Manhattan.

The ceremony, which began just after 8:40am (5:40pm PKT), was designed to be apolitical, with no speeches.

Bereaved family members were reading out the names of all of those killed, with a bell tolling to mark major moments of the attack, which sparked years of US involvement in Middle East wars and bitter controversy over Washington’s human rights record.

“Memorials like this and discussions about those events are an important part of keeping it alive and understanding how we prevent tragedies like this from ever happening again,” said Robert Kafka, a Chicagoan in his 60s visiting the 9/11 Memorial.

Alongside the former presidents was Democratic Mayor Zohran Mamdani, the Big Apple’s first Muslim mayor. He faced a well-organised campaign urging him to stay away, spearheaded by the right-wing New York Post and Trump ally and ex- mayor Rudy Giuliani.

A petition, which has gathered more than 100,000 signatures, accuses Mamdani of associating with unspecified individuals who are “dismissive of American institutions or insufficiently critical of extremist ideologies”.

“It’s concerning to me that the mayor is being treated differently simply because he is Muslim,” city council member Shahana Hanif told CNN.

Mamdani won plaudits for recently revealing thousands of documents showing what city officials knew about toxicity levels of the air in Lower Manhattan following the attacks.

After the initial dust cloud that followed the collapse of the World Trade Centre, months of pollution and lingering dust ensued, causing cancers from which thousands of New Yorkers still suffer today.

‘Toxic air’

Nineteen Al-Qaeda operatives hijacked four airliners on the nearly cloudless autumn day in 2001. Two of the jets slammed into the World Trade Centre’s Twin Towers, causing the iconic 110-storey buildings to collapse.

A third plane struck the Pentagon, while a fourth — believed to have been aiming for Congress or the White House — crashed into a field near Shanksville, Pennsylvania, after passengers fought back.

Beyond those killed on September 11, more than 9,400 other people have died from 9/11-related illnesses, according to the federal program established to provide medical care to those affected.

Some 100 million Americans have been born since or are too young to remember the traumatic day.

Logan Miller, 32, lost his uncle during the attacks, and his grandfather to 9/11-related illness in the aftermath.

“I think the next generation just can’t fathom what actually transpired and how someone could be impacted by that, and so I actually find them asking more questions,” he told AFP.

Huge crowds were expected to gather in Lower Manhattan for the memorial service. The Secret Service, which protects presidents, erected a security ring around the site of the 9/11 Memorial and Museum.

City police Commissioner Jessica Tisch said an anti-drone team would be deployed as a precaution, but stressed there was no intelligence of a specific threat.