Brazil has the world's fourth-highest murder rate

Police said they had met their target of collecting 80,000 guns in under three months, rather than six months.

Brazilians who hand back their weapons are eligible for up to $100.

According to the United Nations, Brazil has the fourth-highest murder rate in the world - about 40,000 people are shot dead each year.

The government had budgeted just over $3m for the buyback programme but has now asked Congress for more money to finance the initiative, which anti-violence groups want extended.

"This campaign could collect up to a million guns, but for that we would need to dramatically expand the number of collection posts and that takes time," Rubem Cesar Fernandes, head of the Rio-based anti-violence group Viva Rio told the Associated Press.