An Iranian woman protesting over death by stoning in Brussels
ISIS militants have publicly executed a female activist for criticizing the group in a Facebook post. (representational image).Reuters file

"Come and watch the first death by stoning in this town," read the ISIS invitation to the residents of Bab Al Sham neighbourhood in the northern Iraqi city of Mosul.

The local residents were reportedly asked by the bearded gun-toting militant to participate in the first death by stoning of a man and none of them had the choice of declining the invitation.

The city was captured by the Islamic State militants in June and since then the group has slowly been implementing the strict Sharia laws in the country.

For many in Mosul, it was the first time they witnessed a stoning. A Mosul resident, Abdallah, told Niqash, a local weekly, that it was the most brutal thing he had ever witnessed in life.

"I was told to sit down and there were hundreds of other people doing the same thing, waiting for the Iqamat al-Had [the application of Islamic law]. A circle was formed and there were a lot of masked gunmen around," Abdallah told the weekly.

"While we were watching the militants moving around, collecting stones and organising seating for everyone, two of the masked men dragged a young, blindfolded man in behind them," he said.

The man, identified as Marwan reportedly was being punished for adultery. "He was pleading for mercy and yelling loudly and everyone could hear him screaming. After stoning him they hit him with one big rock and killed him," he added.

The entire execution took only 20 minutes, but the brutality has left a deep scare in the minds of locals. The residents now fear that the first death by stoning is just a start for the group and soon it will introduce crucifixion, beheadings and other such brutalities practiced by the group in Syria.

Earlier in July in separate incidents in a span of mere 24 hours, the Islamic State had killed two women in Syria by stoning over allegations of "adultery."

In one instance, the woman was sentenced to death in a public square in the town of Tabaqaas after her husband blamed her for not being a virgin.

While in another, a 26-year-old woman was stoned to death by the militants over allegations of adultery.