SYDNEY, June 17 (Reuters) - The Reserve Bank of Australia (RBA) is cancelling its operation to buy long-dated government bonds because of technical difficulties, the central bank said on Thursday, as reports surfaced of outages among several commercial banks.

The websites of some of the biggest banks, including the Commonwealth Bank of Australia, were down, leaving customers unable to log in into their accounts.

"We're aware some of you are experiencing difficulties accessing our services and we're urgently investigating," Commonwealth Bank said in a tweet.

The reason for the outage was not immediately clear. (Reporting by Renju Jose; Editing by Clarence Fernandez)