WA Police have launched an internal investigation after a 40-year-old man who was tasered outside a stationery shop in Perth died.

Officers were responding to a robbery about 11:35am on Friday when they found a man "who required urgent medical assistance" on Lord Street in East Perth, police said.

"As police assisted the man he became aggressive and a struggle ensued, with a police officer being injured," a police spokesman said in a statement.

A police hi-vis vest was left on the ground outside the stationery shop. ( ABC News: David Weber )

"A Taser was deployed.

"As the officers continued their attempt to restrain the man he became unresponsive."

Police said officers provided emergency first aid to the man before St John Ambulance took him to Royal Perth Hospital.

"He has since passed way," the spokesman said.

"Detectives from the Major Crime Squad and Internal Affairs Unit are investigating the circumstances surrounding the incident."

Forensics officers remained at Lord Street late on Friday afternoon with the scene and the entrance to the stationery shop cordoned off.

Police have not confirmed whether the man had anything to do with the reported robbery, or what medical assistance he required.

Anyone with information about the incident has been urged to contact Crime Stoppers.