Wearing nuns' veils, condom-shaped hats and all kinds of silly headgear, Brazilians partied in the beer-slicked streets of Rio de Janeiro as its Carnival started in earnest.

Crowds gathered in the historic hilltop district of Santa Teresa 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 revelers in Santa Teresa wore hats shaped liked condoms -- distributed as part of a campaign to promote safe sex. The government has handed out 19.5 million free condoms across Brazil.

The condom means safe sex -- that's a good Carnival message,

said Thais, a long-legged blonde chugging beer with her girlfriends.

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.