PRIME Minister Julia Gillard has expressed Australia's shock at the worst school shooting in American history.
''Australia grieves with America today,'' Ms Gillard said in a statement.
''Like President Obama and his fellow Americans, our hearts, too, are broken.
''We share America's shock at this senseless and incomprehensible act of evil. As parents and grandparents, as brothers and sisters, as friends of the American people, we mourn the loss of children, aged only five to 10 years, whose futures lay before them.
''We mourn the loss of brave teachers who sought only to lead their students into that future but were brutally murdered in a place of refuge and learning.''
She said the nation's thoughts were with the people of America.
''We hold in our hearts the families who have lost loved children and who face grief beyond measure. We think of the families of the teachers. And we hope for the recovery of those injured in body and spirit,'' she said.
Deputy Opposition Leader Julie Bishop echoed Ms Gillard's sentiments.
''A school should be a place of joy, of learning, an environment where teachers and students can be safe and secure,'' she said on the ABC.
''On behalf of the Coalition, I extend our deepest sympathies.''
Opposition Leader Tony Abbott is in Britain.
Ms Bishop said now was not the time for a detailed debate about gun control, which was a matter of enormous controversy in the United States.
But she said the tragedy would inevitably lead to a debate about what could be done to prevent further murders.
''There has to be an end to this kind of senseless killing,'' she said.
''I'm sure there will be a search for the cause and a debate will ensue in the United States about what they can do to stop this kind of tragedy occurring again.''
Media mogul Rupert Murdoch called on US lawmakers to ban automatic weapons.
''When will politicians find courage to ban automatic weapons? As in Oz after similar tragedy,'' the News Corporation chairman and chief executive tweeted, in reference to the laws enacted by the Howard government after the 1996 Port Arthur massacre in which 35 people were killed.
The Queen sent a message to President Obama expressing her shock and sadness upon hearing the news.
''The thoughts and prayers of everyone in the United Kingdom and throughout the Commonwealth are with the families and friends of those killed and with all those who have been affected by today's events,'' the 86-year-old monarch wrote.
British Prime Minister David Cameron said: ''It is heartbreaking to think of those who have had their children robbed from them at such a young age, when they had so much life ahead of them.''
Canadian Prime Minister Stephen Harper described the news as ''awful''.
''The thoughts and prayers of Canadians are with the students and families in [Connecticut] affected by this senseless violence,'' he tweeted.
In a message to President Obama, French President Francois Hollande said he was horrified.
''I wish to express my deep shock and consternation,'' he said.
United Nations Secretary-General Ban Ki-moon condemned the shootings in a message to Connecticut Governor Dan Malloy.
''The targeting of children is heinous and unthinkable,'' he wrote.
The President of the European Commission, Jose Manuel Barroso, said the shootings were a ''terrible tragedy''.
''Young lives full of hope have been destroyed,'' he said in a statement. With AGENCIES