30 men reportedly gang raped a 16-year-old girl then bragged about it on Twitter.

The gang rape of a teenage girl has triggered a wave of protests across Brazil after photos and a video of the shocking crime were posted on social media.

After going to visit her boyfriend in Rio de Janeiro last weekend, the 16-year-old girl remembered being alone with him before blacking out.

Her next memory was of waking up naked in an unfamiliar house surrounded by more than 30 men, many of whom were armed.

It’s believed she was raped repeatedly by many or all of the men, who then bragged about it on Twitter.

A video, which has since been removed from the site, apparently showed her waking up from drug-induced unconsciousness with a man, laughing, saying “Pounded the girl, get it?”

Before it was taken down it accrued hundreds of likes and misogynistic comments but the majority of those who saw it reacted with revulsion.

The girl’s grandmother told a local newspaper she cried after watching it.

“I regretted watching it. When we heard the story we didn’t believe what was happening. It’s a great affliction. It’s a depressing situation,” she said, according to Sky News.

Hundreds of demonstrators met in downtown Rio on Friday night armed with signs saying “Machismo Kills.” and “No means no”.

In Sao Paolo they painted a mural with messages like “My body is not yours.”

Protesters gathered in cities across Brazil to call for an end to violence against women. Source: Getty

Unfortunately, such violent crimes against women are not uncommon in the poverty-stricken country.

Between 1980 and 2010, more than 92,000 women were killed by gender-related violence, according to a study by the Brazilian Center for Latin American Studies.

The authorities have identified several of the alleged attackers and vowed to bring them to justice.

At least one arrest has already been made, News.com.au reports.

"It is absurd that in the 21st century we should have to live with barbaric crimes such as this," the acting president Michel Temer said.

He promised to introduce a federal police force unit tasked with tackling crimes against women.

While it comes too late for the young woman at the centre of the current furore, the alleged victim says she wants justice done so noone has to suffer like she has.

"Today I feel like a piece of trash," she told Rio's O Globo newspaper.

"I hope that no other person ever feels this way."