Hundreds of homemade metal tacks have been discovered scattered throughout Edinburgh Gardens in Fitzroy North, in inner Melbourne.

The barbed spikes, made from twisted wire, were found on Friday by a member of the public who alerted the local council, and police said they were now investigating the incident.

Authorities have since found more than 800 of them throughout the gardens.

Yarra City Mayor Phillip Vlahogiannis called it a "malicious and cowardly" act and warned park users to be careful.

"They're the sort of things that if you throw them, no matter how they land there's always going to be a spike (pointing) in the air," he said.

"It's not like they can lie flat and not be dangerous.

"It's malicious, it's senseless, it's intended to cause injury, you don't put things like that in a park for any other reason."

The tacks had been put in grassy areas and around trees.

Acting Senior Sergeant Mark Alexander said it was an unusual crime and the maximum penalty if convicted was five years.

"It's extremely dangerous, if a cyclist comes off their bike or a young child falls on one of the tacks or picks one up," he said.

He said it was just luck that no-one had been injured so far.

Councillor Vlahogiannis said cleaning crews had been doing their best to get rid of the tacks over the weekend.

"Both manually as well as a magnetic type vacuum device, I guess is the best way to describe [the way they've been collected]," he said.

"Fortunately so far they haven't been found in any of the playground areas where children would be, but again we are being vigilant about that."

He said the motivation behind the act was unclear, but there were similar tacks found at the nearby Rushall train station.

"We want park users to be aware, be vigilant," Cr Vlahogiannis said.

"It's probably not a good idea to be going barefoot in the gardens, probably not a good idea to be letting children wander off...to let dogs go wandering off."