NEW YORK - It appears that Justin Bieber's bulge, as seen in his ad for Calvin Klein underwear, is the real thing.

Following days of speculation, Bieber's team have said that photos of the muscular pop star wearing briefs in the latest ads for the fashion brand had not been altered in any way, the New York Times reported.

There had been talk last week on Twitter that Bieber's sensitive body part had been digitally enhanced for the ad campaign, shortly after the first images of the ads surfaced, including on Bieber's Instagram account, the Times said.

Chatter was fuelled by website BreatheHeavy.com, which posted what it said was an unretouched photo from Bieber's Calvin Klein shoot.

The picture showed a more slender Bieber minus chest hair.

On Saturday, Breathheavy.com posted a statement to apologise and retract the story and photo in question, saying it was responding to a cease and desist letter from Bieber's camp.

It said: "Because BreatheHeavy is not about making anyone feel bad or intentionally stirring the pot (and are definitely not here for lawsuits), we shall retract the story per request.

"Bieber denies the photo is real, and I respect that and will believe him."

It also attached a quote attributed to Bieber's trainer Patrick Nilsson, saying: "I can definitely confirm that he is a well-endowed guy. I sound weird saying that, but yes."

Among those who commented on the Calvin Klein photos were Rhea Durham, the wife of actor Mark Wahlberg, whose 1992 photo shoot for the brand was a direct inspiration for the new campaign.

She had tweeted: "My baby was the 1st and the best. And not to mention... wow the retouching."

Some of the Calvin Klein photos also featured model Lara Stone in seductive poses with Bieber, 20.

He recently said he trains with Nilsson five days a week for about 45 minutes each.