Crowds gathered in the historic hilltop district of Santa Teresa on Friday for one of the most popular binges, the Bloco das Carmelitas. Elsewhere, bars and cafes overflowed onto the streets as the beat of samba drums rose above the throng.

Many of the revellers in Santa Teresa wore hats shaped liked condoms - distributed as part of a campaign to promote safe sex and prevent the spread of sexually transmitted disease.

The government has handed out 19.5 million free condoms across Brazil, drawing criticism from Roman Catholic clerics in the world's largest Catholic nation.

'The condom means safe sex - that's a good Carnival message,' said Thais, a long-legged blonde chugging beer with her girlfriends.

Others wore black nuns' veils.

'The story is that a long time ago, a nun jumped over the wall of the Carmelita convent, down there, so she could dance in Carnival,' said a hat seller named Rita.

The Bloco das Carmelitas social club named itself after the convent but the revellers showed no signs of being restrained by religious considerations.

An estimated 700,000 Brazilian and foreign tourists are expected to join in the five-day fiesta, famed the world over for its extravagant samba parades and dancers dressed in little more than plumed head-dresses and high-heeled shoes. -- REUTERS