The brutal killing of a 14-year-old pregnant schoolgirl and the discovery of her body apparently buried alive in the backyard of her boyfriend's house in northeast Argentina have ignited nationwide protest against "femicide."

An examination conducted by the authorities on Chiara Paez's body showed she died from beatings to the head, face and body, The Huffington Post reported on Thursday.

The post-mortem evaluation on her body also found some amount of a drug used in abortions, which supports allegations that the girl was killed as a result of conflict with her 16-year-old boyfriend and his family over her pregnancy.

Paez's body was found on May 11 under the patio of the house of the family of her boyfriend, who is facing charges of aggravated murder, femicide and forced abortion. He was said to have confessed to the murder when he faced query by prosecutors, in a case that has been in the news headlines in Argentina for weeks.

"The evidence comes from Manuel's (the boyfriend) own statements, who accepted responsibility as being the perpetrator of the crime," Argentina's La Nacion newspaper quoted prosecutor Alejandro Sinopolis as saying.

The parents of Paez's boyfriend, on the other hand, are facing charges as being accessories to the same crimes.

The discovery of the pregnant teenager's body has caused nationwide protests of thousands against femicide, the killing of a woman because of her gender. Argentina has seen 1,808 femicides since 2008, with more than 250 femicides annually since 2010. The trend, which reached a peak of 295 in 2013, does not show any sign of decrease.

Paez's murder, one of the high-profile cases of femicide, sent protesters holding signs saying "ni una menos," or "not one less."

"The deplorable case of this young girl has triggered a reaction in society and has raised awareness about femicides in Argentina. People are saying that's enough, not one more femicide," said Ada Beatriz, head of local women rights group The Meeting House.

"We're saying femicide is not a private, hidden matter but something that affects all of society because when a woman is killed it affects the whole family and children."

In the town of Rufino, 250 miles north-east of Buenos Aires where Paez was murdered, about 7,000 marched and held a vigil last month. Attendees held pictures of the victim and placards that read "Rufino is in mourning."

Since 2009, Argentina has enacted laws for the protection of women but more funds are needed for their implementation.

"More shelters for survivors of domestic violence are needed and a significantly larger budget to implement gender laws," Beatriz said.

Rights groups seek to file a measure that would deprive men convicted of femicide of the right to care for their children after they finish their jail terms.