RIO DE JANEIRO (AFP) - A Brazilian journalist injured while reporting on violent clashes with protesters in Rio was declared brain dead on Monday, highlighting concerns about security just four months ahead of the World Cup.

Television news cameraman Santiago Ilidio Andrade, 49, was left in a coma after being struck on the head by a flare during protests against bus fare increases last Thursday.

Rio de Janeiro's public health office said on Monday that neurosurgeons at Souza Aguiar municipal hospital had declared the married father-of-one brain dead.

"My husband is gone. They have destroyed a solid family," Mr Andrade's heartbroken wife told the Globo television channel in an interview.

A 22-year-old was arrested on suspicion of manslaughter on Sunday after admitting to having handled a flare that later hit the cameraman.

Last week's clashes echoed the massive street protests which paralysed Brazil during the Fifa Confederations Cup last June, which left at least five people dead.

Five others were injured in last week's protests, which began as a peaceful demonstration but exploded into violence, with around 1,000 people battling riot police who fired tear gas to disperse the crowd.

There is widespread anger in Brazil over the billions of dollars of public money spent on preparations for the World Cup and 2016 Rio Olympics at a time when the country is grappling with poor infrastructure and public services.

The latest violence has renewed concerns about security for the World Cup, which protesters have vowed to target once more.

The Brazilian Association of Investigative Journalism said on Monday that 117 journalists had been injured since the outbreak of violent social unrest during last year's Confederations Cup.

Seventy-five of those hurt, including an Agence France-Presse photographer, received injuries resulting from the actions of Brazil's riot police, which has been criticised for heavy-handed tactics.

Last year's protests were triggered after increases in public transport fares, which were eventually suspended in the bigger cities such as Rio and Sao Paulo.

After a brief lull in November, protests have increased in frequency this year, led by a hardcore anarchist grouping known as the Black Bloc.

Although none of the protests have been on the same scale as last year's demonstrations, they have consistently ended in violent clashes with police.

The Black Bloc said in a post on its Facebook page on Monday that it "strongly deplored" the death of Andrade, saying the cameraman had been injured in a "fight for a better country".