Seventy years ago, thousands of American radio listeners fled what they feared was an imminent invasion by space aliens; while others armed themselves in defence against the marauding extraterrestrials.

Radio listeners, many of whom flooded police emergency phone lines, apparently had missed a disclaimer at the start of the broadcast making it clear that events unfolding over the airwaves were fictional.

A headline emblazoned across the top of the New York Times the next day told the story: "Radio listeners in panic, taking war drama as fact."

This year marks seven decades since the historic "War of the Worlds" broadcast unleashed a furore across the country, as Americans by the tens of thousands allowed themselves to be fooled by the radio broadcast's realistic-sounding news bulletins and sound effects.

A Princeton University study a decade later determined that about a million people were affected in some fashion by the scare.

One reason so many people were taken in was the extraordinary calibre of the production. The science fiction radio drama -- now seen as an American classic -- was a reworking of an acclaimed H.G. Wells' story originally set in Britain.

The version broadcast in the United States, adapted by brash and brilliant young actor and director Orson Welles, aired on the evening of October 30, 1938, one day before Halloween. The performers, consummate professionals, were part of Welles' Mercury Theatre.

For his part, Welles, just 23 at the time of the broadcast, two years later went on to world acclaim as the director, producer and main protagonist in "Citizen Kane." The movie earned him an Oscar and has been hailed as among the greatest films of all time.

Thousands of radio listeners who tuned in to War of the Worlds believed that space aliens carrying ray guns were advancing toward New York City. The program, produced by the CBS Radio Network, was set in the rural town of Grovers Mill, just south of New York, in the neighbouring state of New Jersey.

Henry Brylawski, 95, says he wasn't duped by the broadcast, which he said he also knew was fictional, although others in his circle of friends and family were fooled.

"It didn't make an impression on me at all," he told AFP.

"I heard that Orson Welles program and, very frankly, it didn't affect me in any way. I din't think whether there was a fake or not because I knew it was fake."

"The next morning," he said, "I read in the papers about what a sensation the program had been."

Others however were not so discerning. Among those taken in was Brylawski’s girlfriend’s sister, who, he said "was terrified" by what she believed was to be the alien onslaught.

Seven decades later, Americans still mark the historic radio program and the histrionic reaction it unleashed. Later this week the anniversary will be marked by a new recording of the script at Ball State University, in the Midwestern state of Indiana.

Scholars have devoted written tomes in an effort to figure out how and why the public was so readily duped. Some hypothesized that the hysteria was the result of a US public already put on edge by the drumbeat of war elsewhere in the world.

"The 1938 broadcast of 'War of the Worlds' crystallised tensions and fears for one American night," Scott O'Callaghan, author of an essay "War of the Worlds: Why the Hoax Worked," told AFP.

"The prospect of a hostile encounter with the unknown was all too real for the American people in any number of ways, and the radio broadcast let us experience those fears safely, for one hour," said O'Callaghan, an assistant professor of humanities, Southern Vermont College.

"It unleashed a wave of panic, but also seemed to crystallize the fears of the era, coming as it did with the United States poised to take up arms in World War II," he said.

Download the 1938 audio [link=]here[/link]