British rockers Queen, with American Adam Lambert at vocals, had thousands of Brazilians on their feet and chanting "We will rock you!" at Friday night's Rock in Rio concert.

Some 85,000 people crammed into the City of Rock, a huge park built near where much of the 2016 Rio Olympics will take place.

Lambert, 33, belted out such classics as "Bohemian Rhapsody" and "I Want to Break Free" along with veteran Queen rockers Roger Taylor and Brian May, both well into their 60s.

Videos of the late Freddie Mercury, the flamboyant lead Queen singer who died of health complications brought on by AIDS in 1991, flashed on the giant screen during those songs. The crowd went wild with approval.

"Adam Lambert is sensational," said 38-year-old Reinaldo Amand. "It's not a matter of trying to imitate Freddie, but rather to entertain the public."

He would know -- Amand takes on the role of Freddie Mercury in a Brazilian Queen tribute band.

Clad in tight white pants and sporting a well-groomed moustache and a short yellow jacket, Amand was so spot-on that fans flocked to take selfies with him.

Among the concert-goers was Walter Parana, who was one of the 250,000 people who saw Queen perform with all of its original members in Rio during a downpour back in 1985.

"That was the best concert of my life," Parana told AFP. "Everything was full of mud, but it didn't matter. I jumped so much that my shoes came off and I went home barefoot."

One Republic and The Script opened the first day of the event, a seven-day rock extravaganza broken up over two weeks.

Other big names set to perform over the next days include Metallica, Motley Crue, Rod Stewart, Elton John and Seal.