Police in the US are investigating after at least seven family members were reportedly shot dead in Ohio.

Some media outlets are reporting that a gunman is on the loose but a spokesman for the Ohio Attorney General says they are not aware of any arrests or an "active shooter" situation.

There have also been unconfirmed reports that five children are among the dead.

Local schools are on "lockout", with people prevented from entering or leaving, due to the ongoing situation in Piketon - around 120km from Cincinnati.

Ohio Governor John Kasich, a Republican presidential candidate, tweeted that the situation is "tragic beyond comprehension".