Australian federal government on Saturday expressed concern for 10 Australians still unaccounted for in Japan.

Last Friday, a massive 9.0-magnitude earthquake hit Japan, unleashing a 10-meter high tsunami that did extensive damage.

4462 Australians were registered with Australian Department of Foreign Affairs and Trade (DFAT) in Japan with about 3000 of them Tokyo-based.

DFAT said there was reason to believe 10 people still unaccounted for were in the worst affected areas at the time of the tsunami.

"We have not yet been able to confirm their safety," DFAT said in its updated briefing on the situation in Japan, which was released on its website.

"At this point all we know is that we have not been able to contact 10 Australians who we have reason to believe were in the worst affected areas.

"Communications remain difficult, and we are continuing to try to confirm their safety."

There are no reports of Australian casualties. But, earlier on Friday, Foreign Minister Kevin Rudd warned Australians might still be among the dead.

While large numbers of Australians had already left Japan, DFAT estimate between 1000 to 1500 remained in the greater Tokyo area.

DFAT said it would monitor this situation and had planned for a range of contingencies, in particular, DFAT is in close touch with Qantas and other commercial carriers to make sure there is seat availability to fly out Japan on a commercial basis.

It said if it became apparent more commercial flights were needed, plans were in place for Qantas to arrange additional flights within 24-48 hours.

Meanwhile, Australian officials in Tokyo can provide emergency loans to Australians wanting to leave but unable to afford air tickets, as Rudd on Friday said no Australian would be left behind if they could not afford a flight.

In travel advice updated early on Saturday morning, DFAT continues to advise Australians against travel to Tokyo and northern Honshu unless absolutely necessary.

DFAT is also advising Australians in those areas to leave unless their presence is essential.