The 1938 edition of Action Comics #1 featuring caped hero Superman has sold on the Internet for 1 million U.S. dollars, media reported Tuesday.

Action Comics #1 was first published in June 1938 and introduced the crime-fighting superhero to fans, describing how he was born on a different planet and came to Earth. It also introduces his alter ego Clark Kent's love interest, Lois Lane.

The transaction was held by the U.S. auction website Comic Connect. Both the seller and the buyer were unnamed.

Stephen Fishler, co-owner of the website, described it as "the Holy Grail of comic books".

"The opportunity to buy an un-restored, high-grade Action One comes along once every two decades. It's certainly a milestone," he said.

The 1 million dollar price tag is more than three times the previous record of 317,000 dollars that Comic Connect fetched for a lower-grade Action Comics #1 magazine last year.

There are only about 100 copies of Action Comics #1 known to exist. Of those, only two are in as good of shape as the one that sold today. It has a grade of 8.0 (out of 10) which, in comic terms is a VERY FINE MINUS grade.

There are only two of these issues graded so high. Any comic from the late '30s in this condition is considered extremely valuable because of the demand and rarity.