Some of the costumes reflected recent events

Thousands of Brazilians wearing elaborate costumes followed drummers down the streets, alongside lavishly decorated floats.

The festival is traditional in Catholic countries, where it is held before the 40 day fasting period known as Lent that leads up to Easter.

Commercial complaints

However, the increasing sponsorship and commercialisation of the official parade has led some to complain that the true spirit of the carnival is being lost.

Some shunned the main event for more informal - and free - street parades

Critics point to ticket prices for the stadium, which are impossible for ordinary Brazilians to afford.

Now many are holding unofficial street parties instead.

A surprising choice of costume has been that of America's most wanted man Osama Bin Laden, whose face has adorned tens of thousands of masks.

Dengue fever

Striking a sober note amid the high spirits, the health ministry ordered eight million condoms to be distributed during the festivities.

It is also giving out information at more than 100 hotels about dengue fever, as Brazil's sixth epidemic since 1986 has now killed seven people.

Even the King Momo, king of the carnival, was struck down by the fever, although he appeared fit enough to dance at one of the 220 parties due to be held over the next few days.