Crime Gangs Task Force Acting Detective-Superintendent Kym Hand said similarities in the weapons used in both shootings and the parties involved led police to believe they were linked.
He would not confirm the shootings were directly linked to outlaw motorcycle gangs or that the occupants of both houses were known to each other.
"It is a concern that there are people in our community who will resort to the use of firearms and violence in this manner."
Police have discounted links to the shootings and Vince Focarelli, who previously lived in the Enfield house that was peppered with bullets overnight.
"There is no evidence that there is any relationship," Det-Supt Hand said.
"We will look at all the possible scenarios but there are other people living in that premises at the moment."
Det-Supt Hand denied the shootings were indicative of a fresh bikie war.
"The investigation by SA Police in relation to the outlaw motorcycle gangs, on behalf of the community, is ongoing and will continue to be ongoing," he said.
An Enfield house targeted in one of two shootings early this morning was once occupied by former bikie Vince Focarelli, neighbours say.
A person contacted police about 7.15am and reported hearing loud bangs about 2.30am and finding possible bullet holes at the house on Learmonth Tce, which was unoccupied at the time.
It is the same house that was firebombed in July 2010, shortly after Focarelli moved out.
And two associates of the Hells Angels were killed in February 2010 when a bomb they were transporting exploded prematurely less than 100m from the Learmonth Tce house. Focarelli was the target of the bomb.
It was one of two shootings this morning - a house in Seaton was fired at for the second time in four days.
Pictures show the garage door of the Enfield house and front window peppered with holes. Crime Scene investigators have attended the scene and confirmed bullet holes had been found.
Those bullet holes, and casings found at the scene in Enfield, suggest a shotgun and rifle-type firearm were used in the shooting.
The roller door has been peppered with pellets from a shotgun and multiple bullets have also pierced a front window.
This morning the street was cordoned off while police examine the area.
Neighbour Suzanne Jones said she heard up to six gun shots within 10 seconds.
"It (the gun shots) definitely woke me up. It was really loud . . but I was too scared to come outside," she said.
"There has always been trouble in this street for some reason."
A man, who lives in the house with his family, this morning labelled the people responsible for the early-morning shooting as "dogs".
The man, who did not want to be identified, said he had no idea why his family had been targeted.
"I'm not scared (for my own safety) but I'm scared for my family," he told adelaidenow.
The man said his family had been praying at a mosque when the attack happened.
Meanwhile, also this morning shots were fired into the same Seaton house for the second time, four days after a gunman warned its occupants "I'll be back".
Neighbours reported hearing two loud bangs on Pedlar St, about 3.20am, but didn't see or hear any vehicles.
Crime Scene investigators this morning examined bullet holes that pierced the top right and bottom left of the front window of the Seaton house.
Though the occupants have moved out their Housing Trust home, a green Hyundai was still parked on in the front yard this morning.
Neighbour Horst Schultz said he heard two shots that sounded like they came from the same gun used in Sunday's shooting.
"He said he would come back," Mr Schultz said of the gunman's threat to return.
A second neighbour, who did not want to be identified, said they were worried about the second shooting in less than a week on their street.
Police said the incident was again being treated as a targeted attack and not a random shooting.
One of the occupants, Mohammed Hosseini, said on Sunday the masked gunman had warned his family "I'll be back", after rocks were thrown through their front window and one shot was fired through a screen door and into the doorway.