Italy has defended blocking a shipment of coronavirus vaccines to Australia, saying such action towards less affected countries was legitimate while it was facing "unacceptable" delivery delays.

Foreign Minister Luigi Di Maio insisted the decision "was not a hostile act" towards Australia, pointing out that the blockade was carried out under European Union rules.

Rome yesterday revealed it had blocked the export of 250,700 doses of AstraZeneca's Covid-19 vaccine meant for Australia, blaming the shortage of jabs in virus-hit Europe - and the lack of urgent need in Australia.

Asked about the issue at a press conference in Rome, Mr Di Maio cited first the "unacceptable delays" in delivery of vaccines and the threat from the more contagious UK variant of coronavirus sweeping across Italy and other parts of Europe.

"As long as there are these delays, it is right for European Union countries to block exports to countries which are not vulnerable," he said.

Australia's government said the absence of that one shipment would not affect its rollout of the AstraZeneca vaccine that started today.

However, Prime Minister Scott Morrison said he would ask Brussels to review the decision, the first under an EU scheme that began in January.

A company wanting to export doses out of the EU needs to apply to the national government, which can block the export provided Brussels agrees.

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France also warned today that it could block shipments abroad of Covid-19 vaccines, according to its Health Minister Olivier Veran.

Asked by BFM TV if France could follow Italy's move on this, Mr Veran replied: "We could."

Around 6% of Covid-19 cases in France are from the more contagious variants first found in Brazil and South Africa, he added.

Mr Veran also said that France was doing all it could to avoid a new national lockdown, although the government would keep all options open.

He said there were reasons to believe France's Covid-19 situation would improve in four to six weeks' time as more of its population gets vaccinated against the virus.

German Health Minister Jens Spahn said that drug manufacturers "must honour" vaccine supply contracts to Europe, but said Germany had not yet had any reason to stop shipments of shots produced domestically to other countries.

Mr Spahn told a news conference he had not yet been able to speak to his Italian counterpart about a decision by Italy to block a shipment of AstraZeneca's coronavirus vaccine to Australia.

"As of today, we have not had the reason not to authorise the delivery of vaccines to other parts of the world," he said, adding he would always want to coordinate any approach at a European level.

AstraZeneca's vaccine is not produced in Germany, but some of the final product is bottled by IDT Biologika.