A Jordanian man stabbed his pregnant sister to death, allegedly to "cleanse the family's honor," an official said Thursday.

The 25-year-old woman, whom authorities refused to identify, was killed Tuesday by her brother, who slit her throat and inflicted 15 stabs to various parts of her body, said the official, speaking on condition of anonymity.

The case marked the latest incident of "honor killings" - a practice not uncommon in traditional, male-dominated Arab societies where women have been killed, mostly by brothers and fathers for having sex outside marriage, dating, simply talking to men or even for being raped.

The initial investigation showed the woman had married an Egyptian against her family's wishes almost a year ago and had left for Egypt.

"When she returned to Jordan a few days ago to give birth to her child, her brother learned she was in town. He went to her home on Tuesday and killed her," the official said.

The stabbing occurred in the kitchen of the woman's house. After the slaying, the brother called police and waited for them to arrest him, saying he had stabbed his sister with a kitchen knife.

She was already dead when police arrived, and doctors could not save the baby.

The official told The Associated Press that a post-mortem showed the woman was eight months pregnant with a baby boy.

The killing was the fifth reported "honor killing" since the beginning of the year. Seventeen cases were reported in 2003, and 22 in 2002. Many more are believed to go unreported.

The U.S.-based Human Rights Watch issued a report Tuesday accusing the Jordanian government of failing to protect women from male relatives who threaten and kill them in "honor" crimes.

Last September, Jordanian lawmakers rejected legislative amendments aiming to set harsher punishments for honor crime offenders. Under the country's existing penal code, people found guilty of committing honor crimes can receive sentences as light as six months in jail.