A supermarket cashier has died of a heart attack aged 37 allegedly due to three years of mistreatment from her boss.

The worker, named as Monica Vasquez, died at a Lider supermarket, belonging to the Walmart chain, in the Chilean city of Concepcion.

Her workers’ union claimed she had suffered mistreatment in the workplace for three years.

The victim reportedly died of a heart attack in the middle of a working day after being shouted at by her boss, whose identity has not been divulged.

Karen Gonzalez, president of the National Federation of Walmart Workers, said complaints were filed with the company. However, no action was ever taken.

She added: “Workers were very afraid because the boss was always threatening the cashiers that they could be sacked if they talked.”

Gonzalez also explained that Vasquez suffered with mobility problems and had a medical certificate stating that her work should be carried out while seated. However, the boss allegedly made her carry out standing tasks.

Gonzalez said the boss “did not take her condition into account, treated her badly, and violated her fundamental rights”, adding that he “insulted her as a person in front of clients and colleagues”.

Gonzalez said Vasquez, who passed away on 20th January, was mistreated by her superior moments before her cardiac arrest.

The union spokeswoman said: “The boss shouted at her, treated her badly, and sent her somewhere, telling her to move quickly”.

After her death, the store closed and returned to normal operation after a day of mourning.

The supermarket said in a statement: “Walmart Chile deeply regrets the worker’s death. As a company, we activate all protocols in place for this type of event, at the same time we are supporting her relatives in this difficult moment.

“We categorically deny the accusations made by the president of the National Federation of Walmart Workers since there are no Records of any previous complaint made by the affected worker.”

The local authorities have yet to release a statement on the matter.