The fiance of Sweden's Crown Princess Victoria, Daniel Westling, on Sunday denied claims he was seriously ill as a result of a kidney transplant.

Westling, a 36-year-old former gym instructor who underwent the transplant in May, told the daily newspaper Expressen that press reports published Friday and Saturday carried "false information on my health."

Swedish tabloid Aftonbladet claimed Westling had developed an post-operative infection and was secretly receiving medical treatment, potentially jeopardising his royal marriage planned for June 19.

Westling said his recent medical appointments were mere "routine check-ups."

"It is very hard to read such things. People around me have naturally been alarmed," he said, calling for "more respect in future" for his privacy.

A spokeswoman for the royal palace said she had been inundated with worried calls enquiring about the future prince's health, and dismissed the tabloid claims as "absolutely false".

Westling met the 32-year-old princess when she began working out at one of his gyms in the capital. He owns two luxury by-invitation-only gyms as well as several high-end fitness centres in Stockholm.