Tamworth NAB bank forced to close due to physical security threat on all NAB branches across Australia

There's no clarification on exactly what the threat to security was at this stage but a NAB spokesman said the bank was working with police.

"Unfortunately we have had to close our branches temporarily due to a physical security threat," the bank posted on Twitter," he said.

"As always the safety and security of our customers and colleagues is our priority.

"We are working closely with police and will provide an update as soon as we can."

The bank has not determined the location or the exact nature of the threat.

The new $2.4 million NAB branch on Peel Street only opened earlier this year and brings the bank's business and personal facilities under one roof.

Staff at the Peel Street branch were seen on Peel Street after the announcement that the branch would be closed.