Alt-rock duo the White Stripes thrilled dozens of children at a Toronto day camp Thursday afternoon with an impromptu gig that had the youngsters clapping their hands and wriggling in time to the music.

More than 65 children between ages five and 12 sat in a semicircle on the floor to catch a five-song set by bandmates Jack White and Meg White. About 80 adults, including some fans who talked their way through the door, were allowed in the room.

"This is my fifth year here and something like this has never happened before," said 11-year-old Camille, waving his hands for emphasis.

"When I saw them perform, I was like, 'Wow, I really need to download these songs when I get home."'

Adult fans who had heard about the show by word of mouth, text messages and on websites rushed to the downtown YMCA for the show.

Most were turned away by security, who said the concert was just for kids.

Some 100 people, dressed in the band's red, white and black trademark colours, stood grumbling in a hall outside the auditorium and out on the street.

The day-camp show was just the latest in a series of last-minute gigs the Detroit duo has offered before their Canadian concerts.

Each time, they've relied primarily on their website to spread the word, giving as little as 20 minutes' notice for the unorthodox appearances.

On Monday, the pair surprised Winnipeggers with a performance on a city bus and a downtown bridge.

Over the weekend, a Saskatoon bowling alley was the unconventional stage for a 15-minute set and the previous weekend, it was a community centre in Edmonton where 100 fans were treated to a free show.

Youngsters 'got a kick out of' gig: camp worker

But the 30-minute Toronto show was likely played before their youngest audience yet.

"I'm positive that 90 per cent of these kids don't know who they are, but I think they really got a kick out of it," said Ian Campbell, who works for the day camp.

YMCA spokesman Jamie Slater said he thought it was a prank when the band's manager contacted him about the show Thursday morning.

"At first I thought they were joking," said Slater.

"Once I found out that they were serious, I asked them why they chose the Toronto YMCA, and their manager, Gabe, told me he searched the words 'Toronto' and 'fun' on the internet."

The band is touring Canada in support of their latest album, Icky Thump, and Slater said they asked to play for the camp because they wanted to reach a younger audience.

One child was lucky enough to be called up to sing a part of the R&B song I Believe I Can Fly.

"I was very nervous," said eight-year-old Dylan. "I'll tell my brother I sang in a rock band and there was a band in the YMCA and that's all."