Australia's cheeky show of solidarity

They turned up in their thousands – men and women, old and young, gay and straight – with one aim: to get naked on the steps of the Sydney Opera House.

It was all in the cause of art: the American photographer Spencer Tunick had come to the harbourside city to create his latest installation.

Among the 5,200 people who disrobed for Tunick was a heavily pregnant woman who had postponed a planned induction so she could take part. The rest included office workers, doctors and tourists – and all were equal once the clothes came off.

The installation was commissioned by the organisers of the Sydney Gay and Lesbian Mardi Gras, which is currently under way in the city.

Tunick said afterwards: "Gay men and women lay naked next to their straight neighbours, and this delivered a very strong message to the world that Australians embrace a free and equal society."

Art Rush, a 19-year-old student who took part in the mass pose, said: "It doesn't feel sexual, it just feels tribal – a gathering of humanity."

Steven Anglier, who wore a wig so he could stand out, admitted that before the event, he had thought it might be a bit awkward. "But it's funny because when you're naked and everybody else is naked, you feel like you're dressed, because everybody looks the same," he said.

Tunick has produced almost 100 installations around the world. In Mexico City in 2007 he photographed 18,000 people in the main square.