A shooting in a Connecticut primary school has left 27 people dead, including 18 children, many of them as young as five years old.

According to reports, a masked gunman opened fire on a kindergarten classroom at Sandy Hook Elementary School in the town of Newtown.

A student at the school told NBC Connecticut that she heard seven loud "booms" while she was in gym class.

"A police officer came in and told us to run outside and so we did," she said.

A news conference was set to be held at 6pm BST but has been delayed.

Connecticut School Massacre: 18 Children among 27 Dead in Sandy Hook Shooting

A lone gunman opened fire at the Sandy Hook Elementary School, killing 20 students and six adults

Police said that the Connecticut elementary school is no longer an 'active shooting scene'

A woman carries her daughter to safety in Newtown

Distraught pupils comfort each other after 20 children are killed at the Sandy Hook Elementary School

A father is reunited with his daughter outside the Sandy Hook Elementary School in Newtown.

A woman speaks with a Connecticut State Trooper outside Sandy Hook Elementary School.