THE RIO CARNAVAL HAS STARTED!

Rei Momo opens Brazilian carnival.

Watch the carnival

One of the world's biggest carnival celebrations has officially started in the Brazilian city of Rio de Janeiro. Amid beating Samba drums, Mayor Cesar Maia handed over the keys to the city to the Carnival King or Rei Momo. The government is promoting safe sex during the next five days of revelling and is distributing 25m free condoms. On Thursday, a gang caused panic by firing at random in a middle-class Rio district in retaliation for the death of its leader in a fight with police.

While better known for partying and reckless abandon, this year's carnival is being used to push anti-Aids and healthy eating campaigns. "May a condom be your main Carnival costume," said Alex de Oliveira, 33, an architect when not the Carnival king. Mr de Oliveira has had to shed some excess weight to comply with the mayor's anti-obesity campaign.

Some 11,000 police officers will be on patrol in the coastal city, which has one of the world's highest murder rates. Up to 700,000 tourists, 20% from abroad, are expected to visit Rio during the annual festival. Many will pack the Sambadrome, a 700-metre (2,300-feet) avenue where the top Samba groups will parade on Sunday and Monday.

BBC NEWS REPORT.