Australian police said on Wednesday they were investigating sending suspicious packages to embassies and consulates, media reports said included US and British missions.
There were no reports of any injuries.
The Australian Federal Police said in a brief statement: "The emergency services are inspecting the parcels, the investigation is under way in the circumstances of these facts."
Police did not identify any of the embassies or consulates received by the packages. But the Australian newspaper reported that among them were the UK, New Zealand, India, Japan, Pakistan, South Korea, Germany, Greece, Spain, Seychelles, Switzerland, Croatia and Egypt.
Officials in the US and British consulates confirmed that they had received suspicious packages. "We have dealt with the expulsion in accordance with established procedures and in close coordination with the local authorities investigating the incident," a spokesman for the US consulate said.
Australian media reported earlier that the packages were sent to at least nine international missions in Melbourne, Australia's second largest city, including British, Swiss, German and Indian embassies.
Pictures from the Nine News network showed firefighters and paramedics at the Indian and American expeditions in Melbourne.