Apple has achieved a landmark Mac deal in Japan - with a leading banking group there.

Aozora Bank is preparing for an IPO of shares, and has asked Apple to deploy 2,500 Macs across its main office, data centre, and 17 branches. The bank has instantly become Apple's biggest financial industry client in the world, Reuters reports.

"The question for us was how to simplify the environment and bring it forward 15 years in one jump," said Bill Chute, Aozora's chief technology officer and a former tech executive at Citibank, according to the report.

Apple has continued to attract new interest from firms that would never have touched the platform in the days of Mac OS 9, the report explains, and the move to support Windows on Macs seems set to attract more.

Brian Croll, a senior marketing director at Apple, told Reuters that the move to OS X attracted new customers that Apple has never seen before: "We're dealing with government agencies, science and technology firms, even trucking companies," he said.

The bank will use Macs mostly for document and data processing and electronic communications. The bank also uses servers from various firms, including Apple.