The human remains and clothing, some within a bag and some close by, were discovered by a male who was walking through long grass near Lower River Terrace about 10am on Monday.

Acting Detective Senior Sergeant Warren Gibbs said police were appealing for information from anyone who might have seen suspicious activity in the area over the past 12 months.

"As you may be aware, Lower River Terrace is a well-utilised area, it's right near the rotunda as you come down the stairs there," he said.

"We know people use that for exercise, people are often there for events in and around South Bank.

"It's entirely possible that someone may have seen some sort of activity there at that particular location."

Senior Sergeant Gibbs said it was difficult for police to confirm many details or release information about the possible gender or age of the person whose bones were found, or how long the bones had been there.

He said police were not sure if the person had died at the scene, and police were forensically testing the bones and clothing found in and around the bag.

"Some bones were within that bag, some bones were external to the bag as well," he said.

"The area [where] the bones were located, it's not probably a well-travelled area, albeit not far from that is the road and pathway going to the stairs."

The man who discovered the bones had provided a "lengthy" statement to police, Senior Sergeant Gibbs said.

Why the man had gone off-track into the long grass in the first place was not clear, he said, with the man unable to provide a clear answer to police - but "people do unusual things at times", Senior Sergeant Gibbs said.

Four people from the area who had gone missing within a 12-month period were being investigated as potential links to the bones, he said.

"We're making inquiries into any missing person ... we're not making direct inquiries with families [of missing persons] at this point," he said.