Twenty children are among 27 dead after a gunman opens fire at a primary school in Connecticut, US.

Please wait while this video loads. If it doesn't load after a few seconds you may need to have Adobe Flash installed.

The shooting took place at the Sandy Hook primary school in Newtown, Connecticut on Friday morning, as a gunman fired what one witness described as more than a hundred shots.

Police confirmed that 28 people were found dead in total: 20 of them children aged between five and 10, six adults, and the gunman himself. Another adult was found dead near New Jersey, and is thought to have been killed by the same gunman.

One of the dead was the shooter's mother, a teacher at the school, a law enforcement official said. Other reports suggest the man killed in New Jersey hours before the school shooting was related to the gunman.

The incident is thought to be the worst ever school shooting and the second deadliest in US history after the Virginia Tech massacre in 2007 in which 32 people died.

Please wait while this video loads. If it doesn't load after a few seconds you may need to have Adobe Flash installed.

A tearful President Barack Obama said that politicians must "take meaningful action" regardless of politics in response to the mass shooting at a Connecticut elementary school. Clearly moved by the scale of the tragedy, Mr Obama said "our hearts are broken", and said: "I know there's not a parent in America who doesn't feel the same overwhelming grief today that I do."

He added: "We're going to have to come together and take meaningful action regardless of the politics."

The president asked that all official buildings across Washington fly flags at half mast for the next four days.

Connecticut state police confirmed that there were "several fatalities", including children and staff, but Lt Paul Vance said he would not give any further details until relatives and family members had been properly informed.

"It was horrendous," said parent Brenda Lebinski, who rushed to the school where her daughter is in year three. "Everyone was in hysterics - parents, students. There were kids coming out of the school bloodied. I don't know if they were shot, but they were bloodied."

Police confirmed the gunman was found dead inside the building, and two handguns, described as a Glock and a Sig Sauer, and said that the scene is now secure, and described the situation as secure.

Other sources say the school principal and the psychologist may be among the casualties.

The mayor of Danbury, site of the nearest hospital around 3km away, said three victims were being treated there, and were in "very serious conditions".

map of scene

Officers and ambulances rushed to the scene as soon as the first emergency call was recieved shortly after 9.40am. Those initial 911 calls, according to sources, claimed that there was a gunman in the main school office, and many students were trapped in a classroom.

One student who escaped from the school told NBC News: "I was in the gym and I heard a loud, like seven loud booms, and the gym teacher told us to go in the corner, so we all huddled. And I kept hearing these booming noises. And we all... started crying."

She told the station that police officers had told them to run outside and shelter in a fire station, where they were now waiting for their parents to pick them up.

Federal agents, with dogs and weapons drawn, could be clearly seen running into woods behind the school. One teenager, whose nine year old sister was at the school, and was unhurt, said teachers were shaking and crying as they emerged from the building. "Everyone was traumatised", he said.

The school with more than 600 pupils, is in Fairfield County, about 60 miles north east of New York City. The Newtown public school district placed all schools in the area in lockdown as a precaution.

The Connecticut governor, Dan Molloy, is at the scene, meeting with parents and other relatives. His spokesman said his main concern was getting them the information they needed as soon as possible.

The White House spokesman Jay Carney said today was "not the day" to talk about gun laws, although considerable pressure is now building on social media to push for stronger controls, many using the hashtag #todayistheday.

President Obama is on record as saying he intends to crack down on assault weapons, although that would not have affected the handguns used in the Newtown massacre.