Women and children are not exempted from the brutal terror campaign being undertaken by the Islamic State as five women were recently burned alive in Anbar province, Iraq, after they refused to give their children to the jihadist group, a tribal leader who has been fighting the ISIS in Central Iraq reported. The children they were trying to protect were also put to the torch.

Gangs of the Islamist extremist group—which is carving out a caliphate in the Middle East from existing war-torn countries—torched the women together with their sons in front of residents in the Al-Jamiya neighborhood of Heet, a city 31 miles west of Ramadi, said Sheikh Naim el-Kaoud, who heads the al-Bounmar tribes in Anbar, Fox News reported.

Horrible acts like these serve as a reminder to Muslims of the cost of opposing the jihadists, said Ryan Mauro, a national security analyst for the Clarion Project.

"ISIS could argue that jihad—meaning joining ISIS—is obligatory of all Muslims, so the civilians' refusal qualifies them for execution as apostates," Mauro said.

"Acts like these are also effective for ISIS because it reminds [local Muslims] of the price they'll pay for standing up to the group."

More of such acts can be expected by the international community to occur in the future, he added.

"The story from the tribal leader shows that burning civilians alive and ripping sons away from mothers is now accepted practice among ISIS members," Mauro also said. "ISIS justified the burning of [captured] Jordanian pilot [Moath al-Kasasbeh in January] by arguing that Islam justifies the immolation of those who burn Muslims, such as by dropping bombs."

In the area of al-Kaim, ISIS fighters also reportedly murdered two women accused of cooperating with Iraqi security forces. The two were drowned in the Euphrates River.

Women have also been sold into forced slavery, said the Clarion Project, as almost 50 Yazidi girls as young as 10 were auctioned off at slave markets in Syria.

Some were sold for as little as $80.

Many reports of the ISIS' brutality, however, are difficult to confirm.

"Some of it is hard to tell, but in general, this stuff is happening," said Scott Stewart, vice president of tactical analysis at Stratfor. "It's logical, as they have lost the east to Kurdish forces and, dealing with a large increase of Turkish forces at the border, they are really trying to gain back more ground."

US President Barack Obama said the airstrikes against the group will be increased, but he underlined the crucial role of the countries directly affected by ISIS, saying the real defeat of the extremists will have to come from countries they have invaded, the Clarion Project wrote.

He also said that success against ISIS relies on "Muslim communities, including scholars and clerics, rejecting warped interpretations of Islam and protecting their sons and daughters from recruitment."