Blood is visible near the scene of the attack at a North Adelaide restaurant, but the injured party has not been located.
Police say shots were fired about 9:40pm on Sunday at and near Caffe Paesano in O'Connell Street.
They say two men linked to the Comancheros motorcycle club were sitting at the eatery when they shot at a third man, who returned the fire.
Photo: Blood near scene but no victim located by police (ABC: Robyn Powell)
Police are hunting a man in his 30s, who fled west along Tynte Street toward Wellington Square.
Police think there were also witnesses who may have more information.
There have been three shootings in Adelaide in recent days with links to gangs.
Police say the latest had a connection with the late-night ambush on Focarelli, which left him with a leg injury.
When we do propose strong measures in this regard and we receive criticism for them I'd ask members of the public to cast their minds back to the events of this week to remind themselves of why we take these steps
Premier Jay Weatherill
Assistant Commissioner Grant Stevens says those involved in last week and last night's shootings have gone to ground, hampering the investigation.
"This is an incident which is related to the first shooting incident and we are continuing to investigate," he told reporters.
"I will not make any conclusions in relation to whether it's payback or how it is related, but we do have information that is suggesting to us that the people involved are connected with each other."
South Australian Opposition Leader Isobel Redmond is concerned about the number of shootings in public areas.
"Not only do we have an increase in shootings but they're becoming more brazen and more public and more likely to involve innocent civilians caught in the crossfire," she said.
SA Premier Jay Weatherill says a third gang-related shooting in recent days justifies the Government's focus on dismantling criminal gangs.
He says revised legislation to target criminal gangs will go before State Parliament in the new year.
"When we do propose strong measures in this regard and we receive criticism for them I'd ask members of the public to cast their minds back to the events of this week to remind themselves of why we take these steps," he said.