If the latest school massacre doesn't prompt gun reform in the United States, nothing will, Labor frontbencher Anthony Albanese says.
A gunman on Friday US time shot dead 20 small children and six teachers in the small Connecticut town of Newtown, in one of the worst school shootings in history.
Mr Albanese said his heart went out to all affected in the Newtown shooting, which defied belief.
'If this doesn't create some momentum (for gun reform) it's hard to think that anything would,' he told Sky News on Sunday.
Opposition Leader Tony Abbott, who is in London for the Australia-UK-Israel Leadership Dialogue, said he joined all Australians in expressing deep shock and distress at the loss of so many children and teachers.
'The mass shooting at Sandy Hook Elementary school in Newtown was an unspeakable horror,' Mr Abbott said in a statement.
Some teachers had sacrificed their own lives protecting their students.
'If it was not for the heroic actions of school staff many more young lives would have been lost,' Mr Abbott said.
'Their acts of bravery will not be forgotten.'
Prime Minister Julia Gillard said on Saturday that Australia grieved with America after what she called a 'senseless and incomprehensible act of evil'.
'Like President (Barack) Obama and his fellow Americans, our hearts too are broken,' she said.