Four European companies have lost data in an attack from a new HTML virus, it emerged on Friday evening.

According to an alert from Spanish antivirus developer Panda Software, the worm, called Little Davinia, spreads via the internet and potentially wipes out all files on hard disks and network drives.

However, other antivirus companies said they have seen no samples of the virus and none of their customers had been affected.

Panda said the virus began spreading from a "very large ISP" in Spain, which it refused to name. It also declined to name the four companies attacked. Panda initially alerted the ISP to the virus and has worked to remove it from the provider's systems.

Patrick Hinojosa, general manager at Panda, said the virus is potentially more dangerous than the Loveletter bug which caused worldwide havoc last year, because this time users only have to open emails to be infected rather than having to open attachments. The HTML virus code is spread via email messages with no text in the subject box.

The virus affects Microsoft Word 2000 users and is an HTML, VBS email and macro worm programmed in Spain by a virus writer using the signature Onel 2, according to Panda. The author of the Loveletter virus used the name Onel de Guzman.

Little Davinia is triggered when a user involuntarily downloads a document from the internet which opens automatically. This file, which is saved as littledavinia.vbs in the Windows System directory, sends an email message to all entries in a user's address book.

In the text body, the virus inserts the HTML code and connects the user to the web page that acts as a focal point for the spreading of the worm.

Once the Windows registry has been modified in the victim's computer, the virus searches all accessible hard disks, network drives and directories for any files and overwrites them with an HTML code that continuously displays an error window.

On Friday evening US time, a spokesman for fellow antivirus company Symantec confirmed that the worm is currently a "zoo virus", which means it is not yet out in the wild, while a spokesman for McAfee said none of its European customers have been infected.

This morning, UK-based antivirus company Sophos said it had not received any samples of the virus despite repeatedly emailing Panda Software.

Graham Cluley, Sophos senior technology consultant, said Panda is a member of the REVs(Rapid Exchange for Virus Samples) group, which shares samples of new viruses in order to speed up the process of identification and protection. But despite calls for further information, Panda had so far not co-operated.

"They have broken all the rules of Revs and gone ahead and issued a press release about a virus without sharing samples with other antivirus companies," he said.

"Panda seems to have disappeared from the face of the earth," he added. "My message to them is to work with the industry. Most antivirus companies, even arch enemies, work together to protect their customers."