Frances Fitzgerald described the attack as “despicable”, while Nóirín O’Sullivan said the shooting was “a matter of sadness and shock”.
Ms O’Sullivan said the shooting comes on the week of the fourth anniversary of the murder of Detective Garda Adrian Donohoe in north Louth by a cross-border crime gang.
The PSNI officer was shot at a filling station on the Crumlin Road in Belfast around at 7.30pm on Sunday.
Contrary to early reports of a drive-by shooting, PSNI Chief Constable George Hamilton said the shots were fired by a gunman from behind a fence across the road from the station.
He said the shooting was “completely reckless”, as there were people both in the forecourt filling petrol and in the shop.
He said the officer, who was wearing a bullet-proof vest, received gunshot wounds to his right arm and was undergoing surgery.
He said “violent dissident republicans” were the main suspects.
Ms Fitzgerald said the threat to PSNI officers was “severe”. She said there were individuals who were determined to “take this kind of despicable action” and will do whatever was necessary.
She said both the PSNI and the gardaí have had “huge successes” against dissident republicans.
“There is a severe threat by dissident groups and others to the PSNI in the north of Ireland,” she said.
“Both gardaí and the PSNI are working to ensure that, a) that’s prevented and b) that those who engage in that kind of activity are brought to justice.”
Ms O’Sullivan said the shooting was “very concerning” and that her officers worked very closely with the PSNI to combat terrorism.
“It’s always a matter of sadness and shock when we hear about an officer injured on duty in any fashion, particularly when you hear of an officer being shot,” she said.
“It reminds us, of course, of two colleagues, Tony Golden and Adrian Donohoe, whose anniversary occurs this week.”
She said these officers, and all police officers, go out to protect the public and the community.
Speaking at a Policing Authority event, Ms O’Sullivan also responded to financial issues relating to Templemore Training College, highlighted in an internal Garda audit and reported in the The Sunday Times.
“They span back 20 years, so they are very much legacy issues and very much focus on accounting standards that, by today’s standards, wouldn’t be acceptable.”
She said recommendations regarding modern accounting practices were being implemented: “I’m informed there is no misappropriation of money. There is no criminality that has been identified. If there was, we would have taken action.”