For Brett Eagleson, this week's Saudi-backed golf event at Trump National is an affront: it's happening just miles from where hijackers murdered his father on 9/11.

"It's extremely disrespectful, it's hurtful, it's painful," Eagleson, who was 15 when his dad died in the rubble of the World Trade Center on September 11, 2001, told AFP.

The 36-year-old heads 9/11 Justice, a group that accuses Saudi Arabia of complicity in the atrocity -- allegations the Saudi government has denied.

Ex-president Donald Trump's course in Bedminster, New Jersey, less than 50 miles (80 kilometers) from Ground Zero, is hosting LIV Golf's third event this weekend.

Eagleson was among a few dozen relatives of victims and survivors of the Al-Qaeda attacks, which killed 3,000 people, who gathered near the course Friday ahead of the three-day tournament's start.

Fifteen of the 19 hijackers involved in the coordinated attacks on New York and Washington were Saudi nationals. An FBI memo released last year hinted at official Saudi involvement.

Trump himself claimed in 2016 while he was running for president that Saudi Arabia was responsible, without providing any evidence.

"(Now) he chooses to host the kingdom at his course in the backyard where 750 people were blown away," said Eagleson, referencing the number of New Jersey residents killed on 9/11.

"It's incredibly infuriating," he said.

Bankrolled by Saudi Arabia's Public Investment Fund, LIV has sought to lure top golfers from the establishment PGA and DP World tours with contracts that have run into the hundreds of millions of dollars.

Human Rights groups say the venture is a "sportswashing" exercise being used to boost Saudi Arabia's international reputation. Organizers insist their intention is to boost golf's popularity worldwide.

Avid golfer Trump has emerged as a vocal advocate for LIV, urging players to "take the money" and sign with the circuit.

Trump played in Thursday's pro-am at Bedminster, alongside two of LIV's highest-profile recruits -- major winners Bryson DeChambeau and Dustin Johnson.

He brushed off criticism from 9/11 families in an interview with the Wall Street Journal last week.

'Money over morality'

But Eagleson says Trump's involvement will hurt him politically as he mulls whether to run for the White House again in 2024.

"Some of our biggest 9/11 advocates are family members of FDNY and NYPD. And those have been some of Trump's biggest supporters. Well, not anymore," he said.

LIV organizers have said previously that 9/11 families "have our deepest sympathy," but that "we believe golf is a force for good around the world."

For Tim Frolich, who was injured on 9/11, the tournament has reopened old wounds.

"I had trouble sleeping last night, just the anger," the 58-year-old told AFP as relatives held up photos of their late loved ones and wore T-shirts saying "never forget."

Eagleson's father, Bruce Eagleson, was at a meeting on the 17th floor of the South Tower when hijackers slammed United Airlines Flight 175 into the skyscraper. He was 53.

Eagleson says his father was a huge golf fan whose favorite player was Phil Mickelson, one of the first players to defect to LIV.

"I don't know how he lives with himself," Eagleson said of Mickelson. "He's literally choosing to take the money over any sense of morality."

More protests are planned for upcoming LIV events in Boston, Chicago and Miami, the latter tournament being held at another Trump course.

"We're not going away anytime soon," said Eagleson.