AMMAN, Jordan —  A man who is suspected of drowning his 22-year-old sister for having an extramarital affair was charged Monday with premeditated murder, a judicial official said.

The unidentified woman's brother beat her with the help of his family Saturday and then took her to the Dead Sea where he drowned her, said the official who spoke on condition of anonymity because he was not authorized to talk to the media.

The state prosecutor also charged the woman's parents and another brother Monday with assisting in the murder by knowing about it and beating the woman before she died, the official said.

The woman was killed after an unidentified man was seen leaving her house, the official said.

An average of 20 Jordanian women are killed by relatives every year in so-called honor killings in this tribal-dominated society.