A woman in Montana, US, has allegedly broken into her ex-partner's house with a machete, told him to take his clothes off and forced him to have sex with her.

Police says Samantha Ray Mears, 19, has been charged with aggravated burglary and assault with a weapon after the incident at her ex's home last week.

She has also been charged with several misdemeanours.

The couple reportedly dated for seven years before breaking up.

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Mears broke into her former boyfriend's house on Friday, while he was away.

He returned to the home while she was still inside and she confronted him with the machete, demanding he take off his clothes and lie on his bed.

The man, fearing for his life, complied and Mears is said to have removed her clothes and climbed on top of him.

She then forced the man into sexual intercourse, while she kept holding the machete.

The man reportedly tried to stop her but she refused and bit him on the arm.

Once finished, she allegedly sat on the bed naked, brandishing the machete. The ex-boyfriend was, at this point, able to take several photos of her, which the police are now using as evidence.

Following sexual intercourse, the pair got into an argument and Mears is accused of deliberately urinating on the man's bed.

This is not the first time Mears has been arrested for violence against the same man.