President Obama: 'We haven't yet done enough'

US President Barack Obama has marked the anniversary of the Sandy Hook school shootings by urging Americans to push for tighter gun control.

He said the United States had to "do more to keep dangerous people from getting their hands on a gun so easily".

Twenty children and six school workers were killed at the elementary school in Newtown, Connecticut, a year ago.

Commemorations are being held in the US to mark the first anniversary of the massacre at Sandy Hook elementary school.