Pop superstar Taylor Swift said on Friday it was "excruciating" for her to watch fans struggle to secure tickets for her upcoming US tour after she had been assured that Ticketmaster could handle large demand.

The New York Times reported that the US Justice Department was investigating whether Ticketmaster parent Live Nation Entertainment had abused its power over the multibillion-dollar live music industry.

Live Nation Entertainment said late on Friday that it takes its responsibilities under the anti-trust laws "seriously" and "does not engage in behaviors that could justify antitrust litigation."

The investigation appears to be broad and began before this week's botched sale of tickets to Swift's tour, the Times said on Friday, quoting anonymous sources. The Justice Department declined to comment.

Many people hoping to land seats for Swift's Eras tour, to her first concerts in five years, said they waited hours and were repeatedly kicked off the Ticketmaster website during presales this week.

Swift said on Instagram it was "excruciating for me to just watch mistakes happen with no recourse."

She said she was "not going to make excuses for anyone" because her team had been assured multiple times by ticket sellers that they could handle a surge in demand. Ticketmaster offered seats for most shows on the 20-city, 52-date US stadium tour from March through August.

Ticketmaster said late on Friday it wanted to apologize to "Taylor and all of her fans - especially those who had a terrible experience trying to buy tickets."

The company said it is working to shore up its technology "for the new bar that has been set by demand for the Taylor Swift's Eras Tour".

SeatGeek sold tickets for a handful of performances in Texas and Arizona and also reported long waits, urging fans to "please be patient."

SeatGeek did not immediately respond to requests for comment on Friday.

Earlier in the week, Ticketmaster said it experienced unprecedented interest in Swift's tour from millions of people and worked quickly to resolve technical problems during the presales. It canceled sales to the general public scheduled for Friday.

Swift said it was "truly amazing" that 2.4 million people had bought tickets, "but it really pisses me off that a lot of them feel like they went through several bear attacks to get them."

The "Anti-Hero" singer said she was "trying to figure out how this situation can be improved in the future."

Ticketmaster has angered artists and fans periodically for decades. In the mid-1990s, the grunge band Pearl Jam decided to tour without using Ticketmaster but found handling ticket sales on its own too unwieldy and returned to the service after 14 months.

Live Nation and Ticketmaster merged in a 2010 deal approved by the Justice Department over opposition from some lawmakers and musicians who worried the combined company would become too powerful.

Chaos around the Swift tour prompted calls for the US government to break up the company. Antitrust experts said that argument could find a far more receptive audience than in the past, though it would involve a lengthy process.

Asked if Ticketmaster needed more scrutiny, White House spokeswoman Karine Jean-Pierre said President Joe Biden was a "strong proponent of increasing competition in our economy."

She cited a previous Biden comment that "capitalism without competition isn't capitalism. It's exploitation."

For those who did not get tickets to the Eras tour, Swift said her hope was to provide "more opportunities for us to all get together and sing these songs."