As many as 15,000 Americans are on various "kill lists" that the Islamic State (ISIS) terrorist organisation has put out, with many of them not knowing that they have been marked for death.

Writing for Charisma News, author Michael Synder says some of those who are in the kill lists have been notified by the FBI. However, many have not received FBI notification and are unaware that they have been marked for death. Since the lists are not publicly available, Americans would not know whether their names are on the kill lists.

Circa News was able to obtain samples of the kill lists and found out that of the 24 people marked for death whom they contacted in Texas, 22 of them did not know they were on such a list.

Synder says last week, he was contacted by someone who told him that the FBI had informed him that he and his wife were on the ISIS kill lists.

Even more alarming was their discovery that other members of the couple's church—including their pastor—are also on kill lists.

Where did ISIS get those names?

Synder says the terrorist group apparently got the names from church directories posted on the Internet, "and so now an entire church has ended up on an ISIS kill list."

Islamic terrorists are not afraid to target and kill innocent people in western Europe and the United States as proven by their attacks in Orlando, Dallas, Nice, and Baton Rouge, Synder says.

He urges churches to start taking security a lot more seriously. He cites a recent report about a 21-year-old Islamic radical who purchased a gun and admitted to police that he planned to go into a Detroit megachurch and start shooting people inside on a Sunday morning.

After he was arrested and subsequently charged in court, the suspect told authorities that since he could not do his jihad in the Middle East, he intended to "do my jihad over here."

The members of that church in Detroit should be thankful that the authorities were able to stop that plot in advance, "because the carnage would have been off the charts," Synder says.