A 14-year-old boy has been arrested in the US state of Alabama after shooting dead five members of his family.

Limestone County Sheriff's Office says the teenager "confessed to shooting all five members of his family" on Tuesday.

The five people were shot at a house in the town of Elkmont, with three confirmed dead at the scene.

Two were airlifted to hospital in a critical condition, but died later.

Police say the 14-year-old, who called them, was interviewed and confessed to the shooting.

He is currently assisting investigators in locating the 9mm handgun that was used.

The boy told officers he tossed it nearby.

UPDATE: The two subjects in critical condition have died. The 14-year old caller was interviewed and confessed to shooting all five members of his family in the residence. He is currently assisting investigators in locating the weapon, a 9mm handgun that he said he tossed nearby.

— Limestone Sheriff (@LimestoneCoSO) September 3, 2019

The killings follow a series of mass shootings in the United States, including one in Texas that left seven people dead and 22 wounded - including a toddler.

Last month a gunman killed 22 people and wounded another 24 in El Paso, Texas - while another killed nine and injured 27 in Dayton, Ohio.