Five steak knives have been found buried in the sand at the new Kershaw Gardens playground in Rockhampton in central Queensland.
The Rockhampton Regional Council is in the process of reviewing CCTV of the area after the discovery.
The council said the knives were lying flat in the sandpit and there were no reports of injuries.
Mayor Margaret Strelow said the knives were found on Thursday morning, three by members of the public and the other two by council staff.
She said a thorough search of the area had taken place and no other knives had been found.
"This behaviour is sickening and malicious, and not normal for our community," Cr Strelow said.
"I hope those responsible think carefully about what they've done and consider if they would really be prepared to face up to what could have been very serious consequences."
Resident Bailey Brown said he and his girlfriend also found two knives in a grassy area in the park the day before.
"We were walking there on Wednesday afternoon and I stood on one — lucky I had boots on and everything," Mr Brown said.
He said he was taking the knife to the bin, when he found a second one with its blade sticking out.
"The blade was sticking out and the handle was hidden," he said.
"They were just your generic steak knife — the ones you'll find when you go to the pub for a feed.
"Kids with bare feet [could] do a bit of damage if they run on them."
He said he had quickly disposed of the knives.
"It's definitely not the best thing to be there," he said.
"It's one thing to litter — at least it's better than a syringe."
The new playground has been extremely popular with families since it opened three weeks ago, attracting hundreds of visitors a day.
It is part of a $16 million redevelopment of an area damaged by Cyclone Marcia in 2016.
It was officially reopened by Premier Annastacia Palaszczuk at a public event.
Cr Strelow said council workers inspected the equipment and double-raked the sand every morning.
"We take the safety of those using our facilities incredibly seriously," she said.
"We are aware of similar incidents taking place elsewhere, with people intentionally trying to make play equipment, sand, and synthetic soft fall surfaces dangerous."
