The attackers have also set up four new domains hosting fake Barclays web pages, some of which also host spoof Volksbank pages.
Antivirus company Panda Software said that 54 per cent of the phishing emails it had detected over the past 24 hours were aimed at Barclays customers.
"The authors of this attack are proving to be more tenacious than usual, considering the huge number of messages and the number of false websites set up and circulated in such a short period of time," said Panda Labs director Luis Corrons.
"The signs are that they have no intention of stopping the attack until they have gathered considerable confidential data, so users should keep their guard up at all times."
A spokeswoman for Barclays said that the bank deals with these kind of attacks every day and is approaching this problem in the usual way.
"This is a constant campaign for us and we are working to close down these sites as quickly as possible," she told vnunet.com.
"Barclays never sends emails asking for security information and we would advise customers not to open emails if they are not sure of the source."
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