Prime Minister Julia Gillard says authorities are not aware of any Australian victims of the United States tornado.
The tornado in the US state of Oklahoma killed at least 91 people, with at least 145 people injured including 70 children.
"I express my condolences and sympathy to the families of those killed and injured in the Oklahoma tornado," Ms Gillard said in a statement.
"Australians will no doubt be shocked by the scenes of destruction caused by this event, with tragic images emerging of the devastation caused to schools, homes and property."
She said the Australian embassy in Washington was making "urgent enquiries" to determine whether any Australian citizens were involved, but none had been confirmed to date.