Police have released a series of images of a man in a grey hooded jumper who they want to speak to over the death of a woman whose body was found in the middle of a soccer pitch in Carlton North on Wednesday.

An image from CCTV footage of a man police wish to speak to. Victoria Police

The images, understood to be taken of the man in the CBD, were released by detectives about sixteen hours after the woman's body was found.

An image of the man police wish to speak to. Victoria Police

Am image of a man police wish to speak to Supplied

Meanwhile, police will patrol Princes Park around the clock after refusing to rule out a link between the woman's death and the March sexual assault of another woman less than a kilometre away.

The woman's body was found by a passerby about 2.40am in the middle of the popular Princes Park running track, in Carlton North next to Melbourne General Cemetery.

A pair of polished black men’s shoes found metres from the body are understood to be a key part of the investigation, which is being run by homicide detectives.

The woman's body is removed from the centre of a soccer pitch in Princes Park, Carlton North, on Wednesday. AAP

The woman, believed to be in her 30s, was cold and unresponsive when paramedics arrived. She was declared dead 20 minutes later.

It is understood police suspect it may have been a random attack.

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Acting Homicide Squad Inspector Andrew Stamper said police had an “open mind” about the attacks being linked and that his team was working with the sexual crimes squad.

He would not reveal if the woman's body had any injuries or whether she had been sexually assaulted before she died.

A pair of polished men's shoes found metres from the body. Paul Jeffers

Police said a post mortem would be conducted late on Wednesday.

The soccer pitch, which is close to Melbourne University, was in lock-down on Wednesday as police did line searches for clues.

Another woman was sexually assaulted less than one kilometre away, near Royal Park in Parkville, as she walked home in the early morning of Wednesday, March 28, after a night visiting friends.

US woman Jessie was listening to music through her headphones when she was grabbed from behind in a bear hug and dragged to the ground as she passed the intersection of Gatehouse Street and Bayles Crescent about 2.35am.

The 21-year-old from Washington DC says she was pinned down and beaten before being sexually assaulted.

The attacker tried to cover Jessie’s mouth as she screamed for help but several neighbours heard her. She managed to break free and ran to a nearby property where residents called police.

“It was the only time I thought someone could rip me out of this world… I felt like I was fighting for my life,” Jessie said.

“It felt like a big force pushed me to the ground, there was a lot of force. Very quickly he got on top of me… hitting me, punching me, kicking me," she said.

The attacker was described as aged between 25 and 35, with olive skin, a muscular build and average height. He was wearing a blue or grey hooded jumper, grey jeans and runners with white soles.

Police closed off Princes Park for line searches after the woman's body was found on Wednesday morning. Paul Jeffers

Detective Senior Sergeant Brendan Butland said police believed the attack on Jessie was opportunistic and appealed for anyone with information to come forward.

“Jessie was walking from the Royal Parade, Sydney Road area down to the Flemington Road area. We do know people use that park to walk home and commute home. It’s a popular park,” he said.

A computer-generated image of a man police wish to speak to over the Royal Park sexual assault. Victoria Police

Police released a photo-fit image of the man police wish to speak to over the Parkville sex attack, as well as CCTV footage of a man walking along the street.

On Wednesday morning – only an hour after the woman's body was found in Carlton North – police renewed their appeal to help find the Parkville sex attacker.

Following the attacks, north-west division Superintendent David Clayton said there would now be a highly visible police presence at the park "all times of the day and night".

“They [police] will be on foot, they’ll be on bicycles and they’ll be in cars,” he said.

The University of Melbourne has warned its students to be extra vigilant travelling to and from the institution, and said security officers were available to walk students to their cars and to public transport if they feel unsafe.

"In light of recent incidents in the vicinity of the Parkville campus, the University is asking students and staff to please take special care travelling to and from campus," the university said in a statement.

"With exams currently taking place during shorter winter days, we’d especially like to remind students to be vigilant while studying after dark."