RIO DE JANEIRO - The mayor of Rio de Janeiro on Friday handed a symbolic key to the king of Carnivals in a ceremony marking the start of the city's most renowned festival this year.

Various samba schools in the city started their parades in the Sambadrome and in several other parts of the city with almost 500 so-called Carnival blocks.

As one of the most flamboyant celebrations in the world, the Rio Carnival is expected to lure in some 900,000 tourists to stay in the city for the revelry, Rio's tourism management agency said

To cope with the security challenges from the huge influx of visitors, Rio's police department has deployed 14,400 officers to patrol the streets of Rio. Some 2,500 police cars will also be on call during the holiday.

In Brazil's northern city of Salvador, which also has a name for its Carnival celebrations, half a million tourists are expected this year.