At least 26 people, including up to 20 children between the ages of five and 10, have been killed in a mass shooting at the Sandy Hook primary school in Newton, a small town in rural Connecticut.

The gunman, found dead at the scene, was identified by a US law enforcement official as 20-year-old Adam Lanza, who killed his father at home before driving to the school and killing his mother, Nancy Lanza, who worked there, along with many of her young students.

His brother Ryan Lanza, 24, who was initially mistakenly identified by police as the shooter, has been questioned.

Our US correspondent Nick O'Malley has filed a comprehensive wrap of what we know so far. Click here for the latest news

US President Barack Obama wiped away tears and struggled to compose himself as he mourned the dead in the Connecticut school shooting, and promised "meaningful" action to stop gun tragedies.

"The majority of those who died today were children, beautiful little kids between the ages of five and ten years old," Obama said.

"They had their entire lives ahead of them, birthdays, graduations, weddings, kids of their own."