Image caption Travellers who refuse to be screened by full body scanners must undergo extensive hand searches

The head of the US agency that oversees airport screening has admitted that new pat-down inspections are more invasive than previous techniques.

Transportation Security Administration chief John Pistole was testifying to senators amid complaints the checks target sensitive body areas.

Mr Pistole said he understood privacy concerns, but security was paramount.

Meanwhile, footage of a man refusing to have his groin patted down at a San Diego airport has gone viral online.

Public 'back scanners'

Travellers at US airports who refuse to be screened via new full body scanners must undergo an extensive hand search, which include touching of the genital region and breasts.

"I'm frankly bothered by the level of these pat-downs. I've seen them first-hand in airports in Florida," Republican Senator George LeMieux said during a Senate Commerce, Science and Transportation Committee hearing.

He added: "I wouldn't want my wife to be touched in the way that these folks are being touched. I wouldn't want to be touched that way. And I think that we have to be focused on safety, but there's a balance."

Mr Pistole admitted it was important to consider both safety and privacy, adding that most travellers would prefer to fly on a plane with others who were properly screened.

"I recognize the invasiveness of it. I also recognize that the threat is real. The stakes are high, and we must prevail," Mr Pistole said.

While there have been complaints about the new procedure, a new poll out on Tuesday suggested that eight out of 10 Americans support full body X-ray machines being installed throughout the US to help security officials check underneath passengers' clothing.

Over 60 airports in the US are already using the scanners.

Video footage of one passenger's interaction with an airport official this past weekend has already gained close to 700,000 views on the video-hosting website YouTube.

"If you touch my junk I am going to have you arrested," John Tyner, 31, tells a TSA officer in the video.