BUENOS AIRES (AFP) - The brutal killing of a 16-year-old girl who was allegedly raped and impaled on a spike by drug dealers has sparked outrage in Argentina, where protesters took part in a "women's strike" on Wednesday (Oct 19).

Lucia Perez, a high-school student in the resort city of Mar del Plata, died on Oct 8 after being brought to the hospital by two men who said she had overdosed on drugs. But after doctors noticed signs of violent sexual penetration, investigators pieced together a different story.

Prosecutors say the two men drugged, raped and impaled her through the anus, causing pain so excruciating that she went into cardiac arrest and died.

Lead prosecutor Maria Isabel Sanchez could barely hide her disgust.

"I know it's not very professional to say it, but I'm a mother and a woman, and I've seen a thousand things in my career, but nothing equal to this litany of abhorrent acts," she said.

The killing is just the latest incident of horrific gender violence in Argentina, which has seen more than a year of mass marches to protest brutality against women.

Last year in June, protests broke out nationwide over a trio of gruesome killings: a kindergarten teacher whose estranged husband slit her throat in front of her class; a 14-year-old girl whose boyfriend allegedly beat her to death because she got pregnant; and a woman whose former boyfriend stabbed her to death in broad daylight at a Buenos Aires cafe.

In the latest protest, 50 activist groups called on women across the country to go on "strike" at 1pm local time, taking to the streets dressed in black.

One organiser, Ms Sabrina Cartabia, said the goal was to protest against not only Lucia's killing, but a culture that values women less than men.

That is visible in statistics such as the unemployment rate, she said: 9.3 per cent nationally, but 12 per cent for women.

"In a context of social insecurity, with children to care for and no access to economic autonomy, it's much more difficult to overcome domestic violence," said Ms Cartabia, a lawyer for an advocacy group called the Women's Network.

Lucia met her alleged killers a day before her death, when she and a friend approached them to buy a marijuana joint, prosecutors say.

The men - Matias Farias, 23, and Juan Pablo Offidiani, 41 - were known for selling drugs near her school and had prior convictions.

Investigators say they forced Lucia to consume a large amount of cocaine to incapacitate her, then had a violent orgy with her.

"Her nose was purple from all the cocaine they made her take," said her father Guillermo.

"We can't understand such barbarity. It's impossible to understand," said her mother Marta Montero.

Together, the couple led a protest last Saturday in Mar del Plata that drew 1,000 people, demanding the judge deny bail for the alleged killers.

Despite the protest - and a long string of others in recent months - at least four other women in Argentina have been killed by their husbands or exes since Lucia's death.

Nationally, domestic violence kills one woman every 36 hours on average.

Argentina is one of 16 Latin American countries that have written the crime of "femicide" into their penal codes, setting down harsher punishments for the killing of a woman by a man when gender plays a part in the crime.

But the authorities are not doing enough, argued Ms Cartabia, who says Argentine society needs a wake-up call on women's vulnerable place within it.

A decade ago, the activist said, women who suffered domestic abuse took six years to report it on average.

"Today, that average has gone down - by one year," she said.