The accused man has confessed to the murders, police said (Representational)

A man shot his wife, their two children, and six of her family members on Monday and then burned the bodies when he set her family's home on fire in an alleged dishonour killing in central Pakistan, police said.

Muhammad Ajmal committed the attack as revenge for a suspected affair by his wife Kiran, said Imran Mehmood, a District Police Officer for the city of Multan, where the killings occurred. Ajmal returned to Pakistan from Saudi Arabia, where he worked as a tailor, 25 days ago intending to carry out the killings, he said.

Mehmood said Ajmal confessed to the killings.

"This is clearly an honour killing. He saw a picture of his wife with another man and believed she was having an affair," Mehmood said. "He does not repent his actions."

In addition to killing his wife and their two children, Ajmal also killed his three sisters-in-law, two of their children, and his mother-in-law.

Ajmal and his father, who was with him at the time of the murder, are both in custody and have been charged with murder, Mehmood said. Police are searching for his brother, who is also believed to be involved.

The deaths add to the hundreds of women and girls killed in Pakistan each year, according to human rights groups, by family members angered at the perceived damage to their honour, which may involve eloping, fraternizing with men or any infringement of conservative values regarding women.

Kiran's brother Ali Raza told Reuters that Ajmal and his sister were having marital problems and she had recently moved back to Pakistan and was living with her family.

"I am left with just my father, my whole family is gone," he said.

Mehmood said Ajmal has not been assigned an attorney yet and Reuters was unable to contact any of his family members for a comment.

Pakistan adopted legislation against dishonour killings in 2016, introducing tough punishment and closing a legal loophole that allowed killers to walk free if pardoned by family members.

Police in Pakistan's most populous province of Punjab, where honour crimes have been rampant, said recently that the number of such killings had fallen since the law was introduced but rights groups estimate that nearly 1,000 such killings take place annually.