The husband of a pregnant Pakistani woman who was stoned and beaten to death outside a courthouse in Lahore has said he murdered his first wife – a claim that has delivered another twist to a story that has shocked the country.

Farzana Parveen was murdered on Tuesday by more than two dozen attackers, including her brother and father, for marrying against her family’s will. Now Ms Parveen’s husband, Mohammad Iqbal, 45, has admitted he strangled his first wife so that he could marry again.

“I was in love with Farzana and killed my first wife because of this love,” he told AFP. Mr Iqbal said he was spared a prison term because his son, who alerted police to the murder, later forgave him under Pakistan’s controversial blood-money laws. Having made the confession, Mr Iqbal reportedly switched off his phone.

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Pakistan’s Prime Minister, Nawaz Sharif, demanded to know why police apparently stood by while Ms Parveen was killed. Mr Iqbal told Reuters that police did nothing during the 15 minutes the violence lasted. “I begged them to help us but they said, this is not our duty.”

Police deny failing to help the woman and say no officers were there at the time.

“By the time police reached the scene, the lady had been murdered,” said Shafiq Ahmad, chief of police.