SYDNEY, June 17 (Reuters) - The Reserve Bank of Australia (RBA) is cancelling Thursday"s operation to buy long-dated government bonds because of technical difficulties, it said, as reports circulated of internet outages at several commercial banks and major firms. The websites of some of the biggest banks, such as the Commonwealth Bank of Australia (CBA.AX), Westpac Banking Corp (WBC.AX) and Australia and New Zealand Banking Group (ANZ.AX) were down, leaving customers unable to log in to their accounts. The reason for the outage was not immediately clear. "We"re aware some of you are experiencing difficulties accessing our services and we"re urgently investigating," Commonwealth Bank, Australia"s largest, said on Twitter. Representatives of Australian banks did not immediately respond to separate requests for comment. While customers of many banks reported problems accessing their accounts on Thursday, according to outage monitoring website Downdetector, airlines, telecoms firms and the postal service also suffered technical issues. The bond purchase cancelled by the central bank is usually one of three times each week. "Due to technical difficulties, today"s RBA long-dated open market operations auction has been cancelled," the bank said on its dealing page.