Police said the couple, in their early 40s, were killed in a barrage of rocks thrown by relatives of the woman in a village in central Punjab province on Sunday.

“It was a case of honour killing and we have arrested two brothers of the woman,” local police chief Zafar Bokhari said.

Bokhari said the woman’s family was annoyed because of her alleged affair with a man from the same village and planned the murder with the help of other relatives.

About 4,000 people, mostly women, have been killed in deeply conservative rural Pakistan in recent years in the name of protecting family honour when there are allegations of an illicit sexual relationship.

In 2005, President Pervez Musharraf had a law enacted by parliament, which introduced the death penalty for honour killings.