Leaders around the world expressed shock after a gunman massacred 20 small children and six teachers in Newtown, Connecticut.
UN chief Ban Ki-moon wrote to Connecticut Governor Dan Malloy to give his "deepest condolences at the shocking murders,"
"The targeting of children is heinous and unthinkable," he added
European Union diplomacy chief Catherine Ashton shocked at the tragic shooting.
Meanwhile, European Commission Jose Manuel Barroso "deep shock and horror" upon hearing of the massacre at Sandy Hook Elementary School.
"Young lives full of hope have been destroyed," he said in a statement.
"The news is just awful. The thoughts and prayers of Canadians are with the students and families in CT affected by this senseless violence," Canadian Prime Minister Stephen Harper posted on his Twitter account.
The child victims were reported to be aged between five and 10.
"I was shocked and deeply saddened to hear about today's horrific shooting," British Prime Minister David Cameron said.
"My thoughts are with the injured and those who have lost loved ones. 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."
Britain's Queen Elizabeth II sent a message to President Barack Obama:
"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."
French President Francois Hollande also extended his condolences to the victims and their relatives in a message to Obama.
"This news... horrified me and I wish to express my deep shock and consternation," Hollande said.
The foreign ministry also issued a message in which it offered "France's full support to the American people and authorities."
Australian Prime Minister Julia Gillard said "Australia grieves with America today following the mass shooting of primary school children and teachers in Connecticut.
"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."