Police are investigating after two people were physically assaulted at Queens Park on Friday and Sunday nights.
Both victims were lured through the use of a dating app and police are investigating a potential link between the incidents.
Police would not confirm reports it was the LGBTQ app Grindr or the gender of the victims.
One of the victims was in critical care while the other had sustained serious injuries.
Invercargill Mayor Tom Campbell said he was "devastated and horrified" and had never seen anything like that happen in the region.
"You hear about assaults, but I’ve never heard of anything as serious or planned as this."
He advised residents to follow police advice over staying safe.
There were discussions about how to make Invercargill safer, but only so much was possible, he said.
"All the places people could ask to meet, on the beach, Sandy Point, Donovan Park . . . it would be impossible to increase security in all of them."
Southland area prevention manager acting Inspector Mel Robertson said the offenders were taking advantage of people’s trust with the intention to seriously hurt them.
"It appears people are using these apps to lure people to secluded locations at night with the intention to attack them."
They were working to identify and locate the assailants.
She urged anyone who was planning to meet someone from a dating app to choose a public, well-lit location and letting someone trusted know of your movements.
Invercargill City Council manager parks and recreations Caroline Rain said council was committed to safety in the city’s parks.
"In Queens Park, security cameras are installed across public-facing areas and arterial pathways are lit from dusk till dawn every night."
She acknowledged although those security measures were in place, "the parks are open and shared public spaces".
"We are assisting New Zealand police with their investigation into these attacks."
Information can be reported to police via 105, either over the phone or online, including the file number 260510/6480.
