Sharia punishments include amputations

His hanging at a prison in Kaduna, 290 kilometres (180 miles) south of Katsina, was witnessed by relatives of the victims and government officials.

Katsina is one of a dozen northern Nigerian states to have adopted Islamic law over the past two years.

The Islamic court in Katsina had initially sentenced Yakubu to die by stabbing, using the same knife he was alleged to have used to murder his victims.

Reports suggest the Sharia authorities changed their minds to avoid triggering renewed outbreaks of violence between Muslim and Christians in Kaduna, where more than 2,000 people died two years ago during protests against the introduction of Sharia.

Nigeria's sizeable Christian population has opposed the implementation of Sharia, which includes punishments such as amputation for theft, stoning for adultery and flogging for the drinking of alcohol.

In the nearby state of Sokoto, a Nigerian mother of five is facing a sentence of death by stoning after being convicted of having sex outside marriage.

The country's constitution permits executions for serious crimes, although until now none had been carried out since President Olusegun Obasanjo came to power in 1999.