'Our hearts are broken' - Obama

President Barack Obama wipes his eye as he talks about the Connecticut elementary school shooting. Photo / AP

A grieving US President Barack Obama wiped away tears and struggled to compose himself Friday 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."

Obama paused for several seconds, and breathed heavily, several times wiping a tear from the corner of his eye, as he gave his first reaction to the killing of 26 people including 20 children, in the White House briefing room. The shooter also died.

"Among the fallen, were also teachers, men and women who devoted their lives to helping our children fulfill their dreams," Obama said, noting that he was reacting "not as a president, but as anybody else would, as a parent."

"Our hearts are broken today, for the parents and grandparents, sisters and brothers of these little children and for the families of those who are lost.

"As a country we have been through this too many times," Obama said. mentioning earlier shooting massacres, in Colorado, Oregon and Wisconsin.

"These neighbourhoods are our neighbourhoods, these children are our children.

"We are going to have to come together and take meaningful action to prevent more tragedies like this regardless of the politics," said Obama, the father of two young girls.

"May God bless the memory of the victims and in the words of scripture, heal the broken-hearted and bind up their wounds."

Obama's remarks, were heard in silence in the normally raucous White House House briefing room, broken only by the furious clicking of cameras as he paused and gathered his emotions.

Earlier, the president ordered US flags on the White House, official buildings and at military facilities to half staff to honour the victims of the school shooting rampage, which he called a "heinous" crime.

The order remains in effect until sunset on December 18, the president said in a proclamation, decrying the attack as a "senseless acts of violence" moments before giving his first on camera reaction to the tragedy.

Obama was informed about the shooting in the middle of Friday morning by his top anti-terror and homeland security advisor John Brennan in the Oval Office.

But officials said it was too early, as details of the outrage were becoming known, to plunge into an immediate debate about whether Obama would back more stringent gun control legislation - a bitterly contested issue in Washington.

He had telephone calls with FBI director Robert Mueller and Connecticut Governor Dannel Malloy to offer condolences and help, Carney said.

In a note of irony, Obama made his statement in the White House briefing room, named after James Brady, a former press secretary who was badly wounded in an assassination attempt on former president Ronald Reagan, who became the spur for new gun control laws.

- AAP, AFP