The lights in downtown Toronto went out Saturday evening as the city marked the third annual Earth Hour.

Among the events that took place in the city was a special free concert at Yonge-Dundas Square, which was powered by green energy.

Earth Hour Unplugged ran for much of the evening and featured Chantal Kreviazuk, Canadian R&B artist Jarvis Church and singer-songwriter Justin Nozuka.

The event was lit by energy-efficient LEDs.

Although some power was used to amplify the performers, the usually-bright lights of Dundas Square's billboards were shut off, according to Keith Stewart, WWF Canada's climate change director.

An estimated 52 per cent of Canadian adults participated in the hour-long lights out last year, according to the agency. And the event continues to grow, Stewart said.

"In terms of participation, the only time you get more Canadians doing the same thing at the same time is watching the gold medal hockey game," Stewart told CTV News Channel Saturday. "We had over 10 million Canadians participate last year. The skylines do go significantly darker."

For those who'd rather spend an earth hour perfecting their downward dog, a number of the city's yoga studios held special classes in honour of the event.

Tula Yoga in downtown Toronto held a special hot yoga class to mark the lights- out event. Plus, proceeds from the $15 fee went to the Toronto Environmental Alliance.

Uptown, the third annual yoga by candlelight in honour of Earth Hour at the Bayview Avenue Big Stretch Yoga Centre sold out ahead of time. The class was also a fundraiser, with the $15 fees going to the World Wildlife Fund.

For Earth Hour, people in countries around the world turn off their lights at 8:30 p.m. local time, sending a blanket of darkness across the globe as the hour moves through times zones.

The event was launched by the World Wildlife Fund in Sydney, Australia in 2007, and aims to reduce energy consumption and bring attention to the dangers of climate change.

The lights out is voluntary and does not affect traffic lights or other safety measures.

WWF worker Andy Riley, who came up with the idea for Earth Hour, hopes this year's event will inspire world leaders to push for a stronger climate change agreement than the one struck at the Copenhagen climate change summit in December.

"What we're still looking for in this coming year is a global deal that encourages all countries to lower their emissions," he told The Associated Press Saturday.