Australia has extended its international border ban for another three months, leaving tens of thousands of Australian citizens stranded abroad.

Federal government officials cited the recent emergence of new coronavirus strains as the reason for the decision.

The extension, which was announced late Tuesday, will continue the ban on all departures and arrivals to and from the country until June. Some citizens will be allowed to leave the country on a case-to-case basis. The extension will mean that Australia will have shut its borders to the rest of the world for a total of 15 months by June.

Federal Health Minister Greg Hunt said that the extension is a "necessary measure" to prevent the more highly transmissible variants of the coronavirus from entering the country.

"The extension of the emergency period is informed by specialist medical and epidemiological advice provided by the Australian Health Protection Principal Committee (AHPPC) and Commonwealth Chief Medical Officer," Hunt said.

Hunt said that AHPPC determined that the new variants of the coronavirus pose an "unacceptable public health risk" to everyone in the country. He said that the extension should mitigate those risks and ensure everyone's health and safety.

Official data shows that there is now a backlog of about 40,000 Australian citizens who will still not be able to return home. The extension means that mandatory hotel quarantine will still be in place and it is expected to remain for the rest of the year.

Because of the limited number of quarantine facilities, most Australians that wants to come home will be asked to pay for their accommodations on top of their quarantine bills.

Prime Minister Scott Morrison has been pressured by the other politicians to increase quarantine caps and to allocate more funds towards a planned economic reopening. Federal opposition and some citizens that have been stranded abroad for months have also called on the government to at least have a safe national quarantine plan in place given how vaccines are now being administered globally.

"When Scott Morrison closed the borders he had no plan for the consequences. A year later, 40,000 Australians are still stranded overseas, the border closure has been extended and there's still no plan for safe, national quarantine," opposition foreign affairs spokesperson, Penny Wong, said.