At least 19 people have been killed in Friday's disaster according to press reports, although the figure is expected to climb.
Mr Swan said the government was monitoring the situation carefully and offered all help to Japan.
It was a truly horrific disaster and the thoughts and prayers of all Australians were with the Japanese people, he said.
"It is still too early to know the full extent of the damage but it is clear that this is a significant disaster," Mr Swan said in a statement.
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"Australia stands ready to assist Japan in any way at this difficult time."
Embassy workers in Japan are frantically working to determine if any Australians have been affected.
Anyone who cannot contact their friends or family can call DFAT's 24-hour consular hotline on 1300 555 135.
