Italy and the European Union have blocked a shipment of the Oxford/AstraZeneca coronavirus vaccine destined for Australia amid a stoush over contract commitments between the pharmaceutical company and the EU.

It is understood AstraZeneca had asked the Italian government to export 250,000 doses from its Anagni plant near Rome to Australia.

An EU official confirmed to the ABC that Italy refused the export authorisation, and the decision was supported by the European Commission.

The ban is believed to be the first time Europe has stopped a vaccine shipment to a non-EU country after it tightened its rules on vaccine exports in January in an effort to secure its own supply.

Under the temporary measures any company based in the EU exporting vaccines will first have to submit their plans to national authorities.

AstraZeneca has been contacted for comment.

It comes amid tensions between Europe and AstraZeneca after the latter failed to meet delivery targets set out in its contract with the EU.

In January AstraZeneca cut its supplies to the EU in the first quarter to 40 million doses from 90 million foreseen in the contract, and later told EU states it would cut deliveries by another 50 per cent in the second quarter.

The company later said it was striving to supply missing doses for the second quarter from outside Europe.

The first 300,000 doses of the Oxford/AstraZeneca vaccine arrived by plane in Sydney on Sunday, with the rollout expected to start in Adelaide on Friday after being batch-tested by the Therapeutic Goods Administration.

Australia has secured 53.8 million doses of the Oxford/AstraZeneca vaccine, 3.8 million of which will be manufactured overseas.

The remaining 50 million doses will be made in Australia in monthly doses by medical giant CSL.

ABC/wires