SYDNEY, Dec 15 (Reuters) - Staff at the Reserve Bank of Australia (RBA) were safe and accounted for gunmen were reported holding hostages in a cafe near the central bank's building in the centre of Sydney.

A spokeswoman said the RBA headquarters in Martin Place was locked down with everyone safe inside.

A police operation was underway in the central business district of Sydney after hostages were being held inside the cafe, where a black flag with white Arabic text could be seen in the window.

Traders in currency markets said the hostage news may have contributed to a dip in the Australian dollar, which was already under pressure from global risk aversion as oil prices fell anew. The local currency was pinned at $0.8227, having hit its lowest since mid-2010 last week.

(Reporting by Wayne Cole; Editing by Paul Tait)