AMMAN (AFP) - A 20-year-old Jordanian stabbed his married sister and smashed her head with a rock after accusing her of "immoral behaviour", a security official said on Friday.

"The suspect stabbed his younger sister 20 times with a kitchen knife before smashing her head with a rock inside the family's home on Thursday night, in Nozha" in east Amman, the official told Agence France-Presse.

"He handed himself over to police and confessed to the crime, claiming that he wanted to cleanse his honour after he found her with a man and because her behaviour was immoral."

According to the official, the mother of one "disappeared" from her house one month ago.

"Police found her with a man in an apartment and kept her in custody before handing her over to her brother on the day of the murder," he said.

"She told him she was hungry, so he went out to get food and when he returned, he found her with a man, he alleged," the official added.

The latest killing came hours after a 24-year-old farmer was charged with premeditated murder over the fatal stabbing of his unmarried pregnant sister.

Between 15 and 20 women are murdered each year in Jordan in the name of "honour". Last year, around 17 such killings were recorded.