A number of consulates have been evacuated in Melbourne.
The developing situation comes just two days after a "suspicious" white powder was found at the Argentinian Consulate in Sydney.
"All our staff are safe and accounted for", said a British High Commission spokesperson.
It was not immediately known which countries' diplomatic missions in the national capital, Canberra, were affected.
Police in Australia are investigating suspicious packages sent to at least ten embassies and consulates in Canberra and Melbourne, including those of Britain, the United States and New Zealand.
One New Zealand official told the ABC their consulate received an envelope full of small plastic bags with what appeared to be concrete and asbestos. "The circumstances are being investigated", said the AFP statement.
A spokeswoman for the Australian Federal Police said: "Police and emergency services have responded to suspicious packages delivered to embassies and consulates in Melbourne today". Suspicious packages may have been sent to up to 22 locations.
At this time we believe the matter is targeted and not impacting the general community.
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"Police and emergency services have responded to suspicious packages to embassies and consulates".
"Victoria Police will work to assist the AFP and other agencies including the [Metropolitan Fire Brigade] with the management and investigation of this issue".
The metropolitan fire brigade and AFP officers attended the incidents, as did paramedics.
However the USA embassy in Canberra was not targeted with a package, a spokesperson said.
There was also an alert of a hazardous material incident at Yertchuch Avenue in Ashwood, in Melbourne's eastern suburbs, where the Swiss consulate is based.
There were at least 17 "hazardous material" warnings listed on the Victoria Emergency website after 1pm, scattered across the city on Collins St, Queens St, William St, St Kilda Rd and Albert Rd.
"It's believed to be non-hazardous, however they're treating it as hazardous", she said.