Security high for Rio revellers

Five days of raucous celebrations kicked off on Friday

The self-proclaimed "greatest party on Earth" has begun in Brazil as the country celebrates its annual carnival.

Tens of thousands of people took to the streets of Rio de Janeiro on Friday night as the revelry got under way.

However security was tight after some shocking examples of violent crime recently, a BBC correspondent says.

Thousands of extra police officers are on duty in Rio, some occupying hillside favellas or shanty towns, others patrolling tourist areas.

The city has seen some horrific violence in recent weeks, including the killing on Tuesday of a leading member of one of the city's samba schools.

Mayor Cesar Maia kicked off the celebrations by handing the key of the city to the carnival king, known as Rei Momo, at a ceremony outside the city hall.

Asked if he thought the recent violence would spoil the carnival atmosphere, Mr Maia said:

Carnival in pictures

"No, quite the opposite. I think that given these unfortunate events, Rio de Janeiro will work past these events to reaffirm its nature and identity as people who are calm, peaceful and happy. Carnival is a good time for this, for us to reaffirm the identity of 'Cariocas' [people from Rio de Janeiro]."

About 180 million Brazilians and hundreds of thousands of tourists are taking part in celebrations nationwide.

Like last year, the government has handed out 25 million condoms as part of a safe sex campaign.