TORONTO (Reuters) - Royal Bank of Canada's <RY.TO> online banking and retail trading platforms, as well as its telephone support system, have been down since Monday morning, with users receiving error messages attributing the failures to "technical issues."

Irate clients of Canada's biggest bank took to Twitter to complain about their inability to access their accounts, execute trades on the bank's website or app, or reach customer service agents, with some pointing out that this was not the first outage experienced by the bank this year.

"We're aware of an issue affecting our online banking and mobile app at the moment," RBC posted on Twitter in response to the complaints. "We're working to get this corrected as quickly as possible. We're sorry for the inconvenience."

RBC did not immediately respond to an emailed request for comment. The bank's shares were down 2% in afternoon trade in Toronto, versus a 1.8% decline in the Toronto stock benchmark <.GSPTSE>.