Tens of thousands of Japanese police are standing guard over bank cash machines today, in a bid to protect pensioners from the growing threat of fraud.

Conmen posing as anything from family members in trouble to tax officials promising a refund have tricked mostly elderly people into transferring more than 25 billion yento their accounts via ATMs in 2007. This year is set to be even worse, police figures show.

About 56,000 police across the nation took part in a campaign to keep guard over cash machines today, because most people's pensions are paid into their accounts on the 15th of each month.

The campaign, which covered about 80 percent of Japan's 98,000 cash machines, managed to prevent at least one 66-year-old woman from becoming a victim, NHK reported.

The fraudsters have taken advantage of the fact that most Japanese people regularly pay bills and make transfers using the ATMs at their banks. But with banks and police trying to clamp down on the problem, an increasing number of cases involve cash being sent by mail, media reports say.