Revelers and Afro-Brazilian men and women thronged the streets of Rio de Janeiro and Sao Paulo as the annual Brazil Carnival 2012 began Friday.

They took part in the annual block parties, known as the Afro Ilu Oba De Min and Carmelitas, one of the many carnival parties to take place in Sao Paulo and in the neighborhood of Rio de Janeiro every year.

The Brazilian Carnival, which is held 46 days before Easter, is marked by samba parades on the streets of Sao Paulo and Rio de Janeiro.

The Carnival, the most famous holiday event in Brazil, is happening from Feb. 17 to 21. Brazil receives about 70 percent of its annual visitors during the Carnival, according to officials.

During the celebrations, people indulge in the practice of eating fatty foods on the last night before the first day of Lenten season (also known as Ash Wednesday), when fasting prevails.

Samba group parade is one of the most significant traditions of the Brazilian Carnival, in which all the country's samba schools compete in various categories of costume, dance and percussion (drumming). Samba schools try to outdo each other with floats, costumes and dancing during the Brazilian Carnival.

Check out below a few pictures of the annual block parties held in Sao Paulo and Rio de Janeiro on the opening day of the carnival.