A Brazilian woman was lynched after a false rumour she kidnapped children for black magic rituals spread on Facebook.

Fabiane Maria de Jesus, 33, was seized on the street and brutally beaten by a mob near a shack in Guarujá, a popular seaside city 70km south of Sao Paulo.

Video footage recorded by onlookers, and subsequently leaked to Brazilian media, shows the housewife lying face down on an unpaved road in the Morrinhos suburb of the touristic town, nicknamed "the pearl of the Atlantic".

As De Jesus lies prone, attackers take turns hitting her and throwing her body around. One man pulls her head by the air before slamming it to the ground.

Another runs over her with a bicycle while a third ties a rope to her wrist and drugs her away, as dozens of people look on.

Police were eventually called and De Jesus was rescued and taken in desperate condition to a hospital, where the she died after two days of agony, according to the Folha de Sao Paulo newspaper.

Airton Sinto, a lawyer for the victim's family, said De Jesus was mistakenly identified as a child kidnapper by netizens commenting on a Facebook page about crime in the area named Guarujá Alerta.

Days before the attack, the page published a post warning its followers of a rumour saying that a woman in the area was abducting children to use for witchcraft rites.

"Whether or not it is a rumour, let's stay alert," the post, which has since been taken down, reportedly read.

It featured a police sketch depicting a woman who commentators identified as De Jesus.

Police say they have no reason to believe De Jesus was involved in kidnappings or black magic. In fact, they claim the facial composite published on the page was that of another person suspected of a 2012 attempted kidnapping in Rio de Janeiro.

Authorities said they have identified five attackers and arrested one. An investigation into Guarujá Alerta has also been opened.