Man and his girlfriend shot dead at property in rural South Australia

A man has been charged with two counts of murder over the shooting deaths of two 19 year olds at a rural property in South Australia. Photo / Tricia Watkinson, News Corp

A man has been charged with two counts of murder over the shooting deaths of two 19 year olds at a rural property in South Australia.

Authorities believe the man shot dead two teenagers – his son and his son's girlfriend – in an alleged double murder.

Officers were called to a rural property in Mount McIntyre, near Millicent in the state's southeast, about 11.30pm on Saturday where they found the bodies of the two teenagers.

A South Australian man is accused of shooting dead two teenagers, one is believed to be his son. Photo / Tricia Watkinson, News Corp

A 46-year-old man, the 19-year-old man's father, was arrested at the scene. He was charged with two counts of murder and will appear at the Mount Gambier Magistrates Court on Monday.

Police said the teenagers live in Adelaide and were visiting the property for a family gathering.

Major Crime detectives and Forensic Response officers flew to the area from Adelaide and are expected to remain at the property all day.

"(We are) treating this as an incident where unfortunately the father is alleged to have killed his son, and we understand that the female involved is the partner of the son," Detective Inspector Campbell Hill told reporters on Sunday.

"We do have people that were here at the time, we are working through and supporting those."

It is not yet known if a firearm has been seized.