Multiple deaths were reported Friday in a shooting at a US elementary school in Connecticut, DPA reported.
CBS News said 27 people were dead, including 14 children. ABC News reported 12 deaths at the Sandy Hook Elementary school in Newtown.
President Barack Obama had been informed and was getting regular updates on the situation, the White House said.
A person believed to be the shooter was among the dead, the Hartford Courant newspaper reported. The school principal and a school psychiatrist were also killed, CNN said.
Police were expected to brief the media shortly.
Details about the alleged gunman and a possible motive were unknown.
The school educates pupils roughly from age 5 to 10.
On Tuesday, three people were killed in a shooting in an Oregon shopping mall on the US West Coast. The 22-year-old shooter used an AR-15 semi-automatic weapon to kill a woman, 54, and a man, 45, before killing himself.
A 15-year-old girl was critically injured in the shooting that took place in the food court at the Clackamas Town Centre mall.
Two other shootings in public places have occurred in recent months. One left 12 people dead and 59 wounded in July in a packed cinema in the Denver suburb of Aurora, Colorado, during a midnight showing of the Batman sequel. In the other, six people were killed in a Wisconsin Sikh temple; the assailant then killed himself.