Crown Princess Victoria and Prince Daniel of Sweden tested positive for COVID-19 on Thursday.

The Swedish royals isolated themselves on Wednesday after the Crown Princess experienced cold symptoms, with their diagnosis being confirmed one day later, a statement confirmed.

"The Crown Princess and Prince Daniel are doing well under the circumstances with only mild symptoms," the Swedish royal court said.

"Immediately after the symptoms of illness appeared, The Crown Princess, Prince Daniel, Princess Estelle and Prince Oscar were quarantined at home."

The couple's diagnosis comes just days after they celebrated their son's fifth birthday.

Princess Victoria shared some adorable photos of her son on Instagram to mark the special occasion. Young Prince Oscar was joined by the family's cavoodle puppy Rio in one of the portraits taken by Kate Gabor inside Haga Palace, Solna. 

Swedish royals2 

The Swedish royals are isolating at home

The five-year-old looked smart in a grey patterned jumper with his white shirt collar poking through the top and his brunette hair swept away from his face.

The photos also inadvertently gave fans another peek at the beautiful royal interior, including a gold-trimmed chair, wooden floorboards, a crystal chandelier hanging from the ceiling and giant windows flooding the property with natural light.

In another wintery snap taken in the grounds of the royal residence, Oscar and his older sister Estelle wore matching blue puffer jackets and warm hats as they sat in the thick snow.

"Today, H.K.H. Prince Oscar's 5th birthday," the caption simply read, and it wasn't long before royal fans left birthday messages.

"Grattis Oscar, beautiful photos," commented one follower, and a second added: "Happy birthday Prince Oscar."

Prince Oscar was born on 2 March 2016 at Karolinska University Hospital in Solna, Stockholm. He is a grandson of King Carl XVI Gustaf and Queen Silvia and is currently third in the line of succession to the Swedish throne after his mother Crown Princess Victoria and older sister, Princess Estelle.