A man is in custody after a woman’s body was dumped on a busy street outside an apartment block in Perth today.

Police said a man, believed to be known to the woman, approached paramedics with the body in his arms on the Grand Boulevard in Joondalup at 9.45am (11.45am AEST).

Police said he asked paramedics for help then took off.

WA Police Detective inspector Jayd Morawski. (9News)

Authorities are investigating the cause of the woman’s death and whether there are any suspicious circumstances.

The woman has not yet been formally identified.

Police launched a significant investigation involving major crime detectives before tonight announcing a 35-year-old was in their custody and assisting with their investigation.

Earlier, WA Police Detective Inspector Jayd Morawski urged the man to contact police.

“We want to provide a full picture, so we know exactly what occurred, so we can provide answers to the family and provide answers to the state coroner,” Morawski said.

“There is a conversation required, there are answers that need to be given and he can provide those answers, so we’d like him to do that on his own volition.

“Ultimately, we have a lot of resources and a lot of technology that we can deploy to find this person.

“We know who he is and the best thing he can do is hand himself in to police.”

Police do not believe there is any threat to the wider community.

“This is an isolated matter and as such, we don’t think the community is at any risk,” Morawski said.

Police are also seeking CCTV and dash cam footage from the Grand Boulevard between 9.30am and 9.45am today.