A man carrying a backpack has been arrested after he was spotted behaving erratically outside Crown casino.

Police responded to a report and arrested a 55-year-old man after evacuating the complex, however, they refuse to say what was in backpack or if the man had made threats.

A section of the Southbank frontage of Crown between Clarendon and King Street has been closed off, with large groups of staff from the casino’s restaurants gathering outside the Melbourne Exhibition Centre.

Clarendon Street has re-opened, but the walkway over the Yarra is closed.