A reveler of the Sao Clemente samba school performs during the first night of Carnival at the Sambadrome in Rio de Janeiro on Monday. Photo: AFP

Rio's Carnival burst into top gear late Sunday, adding a sultry yet competitive edge to the event as elite samba schools compete for the champions' title at the fabled Sambadrome.

More than 70,000 people, including foreign tourists who paid hundreds of dollars for a close-up view, watched as dancers and drummers turned the arena into a blur of sensuality and joy.

A dozen Special Group schools, each consisting­ of several thousand scantily-clad dancers and drummers, are chasing the prestigious­ title.

The Sambadrome, designed by Brazilian modernist­ architect Oscar Niemeyer and located in the heart of the iconic city, is celebrating its 30th anniversary.

As the schools entered the arena to strut their stuff, the parade ground along the famed 720-meter Sabucai Avenue shook to the pounding samba beat.

"When I turned into the avenue the ground literally shook," said Carnival "sovereign" King Momo, who Friday declared the festivities open and ordered joy by decree.

"The sheer energy was impressive - it's a very happy night," he said.

However, the arrival of Carnival doesn't automatically mean everybody is happy. During the celebrations a group of sanitation workers demonstrated for better pay outside city hall Sunday as trash piled up high in the streets.