British detectives have made the first arrests in Europe to tackle a "trojan" computer virus which is believed to have infected tens of thousands of computers across the world, London police said yesterday.

The ZeuS or Zbot trojan, a type of sophisticated malicious computer programme, has been used to collect millions of lines of data from machines allowing those responsible to obtain a mass of personal information. The Metropolitan Pol-ice said the trojan was configured so that once installed in an affected computer, it recorded users' bank details and passwords, credit card numbers and other information such as passwords for social networking sites.

The financial gains for the criminals and the potential losses to individuals and institutions affected were very substantial, detectives said.

Police said a man and a woman, both aged 20, had been arrested on November 3 in Manchester. They have been released on police bail pending further inquiries.

The ZeuS trojan is a piece of malware used increasingly by criminals to obtain huge quantities of sensitive information from thousands of compromised computers around the world.