A new computer virus dubbed the "Love Bug" has forced email servers to shut down in Europe and is now spreading wildly in the US.
The virus quickly spread across Europe Thursday before invading the U.S. as the workday dawned.
The lower House of Commons shut down its email system for about two hours on Thursday to safeguard against the virus, which has been likened to the Melissa virus, which caused chaos in the United States last year.
The new virus originates in an email entitled "I love you." Once the attachment is launched, the virus sends copies of the same email to everybody listed in the user's address book.
According to anti-virus software company GFI, the virus affects Microsoft Outlook users, and is also being spread over popular chat program IRC.
The Melissa virus operated similarly, infecting about a million computers, clogging whole networks in the United States, and causing $80 million in damage.
Anti-virus firm Symantec said it had already released an update to its software to combat the virus, but warned computer users not to open any "I love you" messages.
British Internet service provider Freeserve said it had set up a filter to screen out any amorous emails with the words "I love you."
Anti-virus company F-Secure issued an email alert on the virus. "This worm spreads at an amazing speed", said Mikko Hypponen, manager of anti-virus research at F-Secure. The email said the company had reports from over 20 countries.
"We estimate that total number of infected machines is already in tens of thousands. This epidemic might exceed Melissa in both speed and destructiveness."
Dutch IT consultancy Ordina Beheer NV was also hit by the virus on Thursday.
Ordina confirmed it had received emails containing the virus, but said it had shut down its network servers to avoid passing it on to customers or other correspondents.
The virus reportedly originated in the Philippines and has also been nicknamed the "Killer from Manila," but anti-virus experts do not hold out much hope that the culprit who created it will be found.
Reuters contributed to this report.