A fake email invitation to this year's Nobel Peace Prize ceremony is currently circulating and carrying with it a virus capable of infecting the computer of anyone who opens it, computer security experts warned.

Appearing to come from the Oslo Freedom Forum, a group with no direct Nobel ties, the email includes a PDF attachment containing a so-called "Trojan horse," allowing hackers to take control of victims' computers, reported the Contagio Internet security blog (http://contagiodumb.blogspot.com).

"Dear Sir/Madame. I enclose a letter from Oslo Freedom Forum founder Thor Halvorssen inviting you to join him in Oslo for the December 11th (sic) prize ceremony. Let me know if you have any questions," the email reads.

The 2010 Nobel Peace Prize, which was attributed in October to jailed Chinese dissident Liu Xiaobo, much to the distaste of Beijing, is to be handed over at an official ceremony in Oslo on December 10.

"We don't know who launched the attack, or who the target was," the F-Secure computer security group said on its website.

According to daily Aftenposten's online edition, Nobel Institute director Geir Lundestad has meanwhile been the target of a cyber attack through an email that appeared to come a technician at a IT company working for the institute.

The email reportedly contained a link requesting him to type in his user name and password, but Lundestad had become suspicious and alerted Norwegian data security authorities.

"There is someone trying to infect the Nobel Institute," the head of the Norwegian Computer Emergency Response Team, Christophe Birkeland, told the paper.

"There is a lot to indicate that the same person is behind these attacks," he added.

The Nobel Peace Prize website (www.nobelpeaceprize.org) was also the target of a cyber attack two weeks ago, with the last IP address used in that attack belonging to the National Chiao Tung University in Taiwan.

However, there is no way of knowing if the attack actually came from there, since hackers often used many computers to hide their traces.