Bill O'Reilly Nun Story - FOX News host Bill O'Reilly has been accused again of fabricating a report, this time about witnessing four nuns being executed in El Salvador during the country's civil war in the 1980s.

The claims that O'Reilly fabricated the report, in which he said that "he saw nuns get shot in the back of the head" in El Salvador, was made on Wednesday by liberal media watchdog Media Matters for America.

This is the second time in as many days that the conservative host has been under fire for 'an apparent fabrication' in his reports. On Tuesday, Media Matters questioned O'Reilly's report where he claimed to have witnessed the 1977 suicide of a friend of JFK's shooter Lee Harvey Oswald.

The onslaught of questions about the authenticity of O'Reilly's reports began after Mother Jones disputed his Falklands War story, where he claimed to have been involved in a 'combat situation' while reporting from Buenos Aires when protests erupted.

According to Media Matters, Bill O'Reilly claimed to have "seen guys gun down nuns in El Salvador." He claimed he "was in El Salvador and I saw nuns get shot in the back of the head," while working with CBS News.

Reports indicate that O'Reilly may have been referring to a December 1980 case where Salvadoran national guards executed four nuns.

However, the liberal media watchdog cited a University of Florida professor of religion who said "no priests or nuns were killed in El Salvador for more than eight years after January 1981."

Professor Anna L. Peterson also said that "thousands of lay Christians activists continued to die at the hands of death squads and the military."

In O'Reilly's book, The No Spin Zone, he claims to have only started covering the El Salvador civil urest in 1981 after he became a CBS News correspondent.

On Wednesday night, Bill O'Reilly responded to the allegations saying "While in El Salvador, reporters were shown horrendous images of violence that were never broadcast, including depictions of nuns who were murdered. The mention of the nuns on my program came the day of the Newtown massacre (December 14, 2012.)."

"The segment was about evil and how hard it is for folks to comprehend it. I used the murdered nuns as an example of that evil. That's what I am referring to when I say ' I saw nuns get shot in the back of the head.' No one could possibly take that segment as reporting on El Salvador," he said.