Irish singer Niall Horan has admitted feeling "trapped" at times while he was part of the former British boy band One Direction.

The 27-year-old singer opened up about his time with the band, which originally included Liam Payne, Harry Styles, Zayn Malik and Louis Tomlinson apart from Horan, during a conversation with Dermot O'Leary for the show, "People, Just People".

"In the UK it was nuts," Horan said of the fan frenzy that followed the group's appearance on "The X Factor" in 2010. "Going and doing signings here and there, bits and pieces like that -- that was the first sign of it. (There was) banging on car windows (and swarms of fans)."

"I remember getting to Milan on the first day and thinking, ‘This is a different level.' There were thousands (of people). Everything in Italy, it's a bit more dramatic. That was when I remember thinking, ‘This is nuts'," he added.

Horan explained that since the group was still in their teenage, it was difficult to come to grips with fame and attention that came their way.

"I struggled with the idea of, ‘Why won't you just let us out?' We just want to go for a walk," he said, adding "But you can't get inside the brain of a fan. Now I completely get it, but at the time, you're like, ‘You're our age. Just let us out."