Hideki Kaji, known for having a particular fondness for the Scandinavian countries, was in Malmö to record a music video.
The world-renowned popstar was recording on the street in the Kroksbäck area of the southern Swedish city when the robbers struck.
When the film team took a break and the cameramen left the site to photograph their children who had also accompanied the team, Hideki Kaji was left to guard the equipment, dressed as a pineapple.
"Three men then walked towards him, beat him up and robbed him. He was hit so hard that he lost a filling. He then passed out. When he woke up camera equipment worth a total of 20,000 kronor ($2,500) had been stolen," Mattias Attin at Malmö police told local newspaper Sydsvenskan.
Police had by Sunday morning been unable to apprehend anyone in connection with the attack.
Hideki Kaji is a regular visitor to Scandinavia and has recorded an album in Sweden under the celebrated Tambourine Studios label. Some of his hits have included "My Favourite Tofflor", "Suddenly Sibylla" and "Ramlösa".