Norway's Crown Princess Mette-Marit will likely need a lung transplant as her health has worsened in recent months, the country's royal household has said.

Axar.az reports that the princess, 52, was diagnosed with pulmonary fibrosis in 2018. The degenerative disease creates scar tissue that stiffens the lungs, making it difficult to breathe and for oxygen to enter the bloodstream.

Tests in autumn showed "a clear worsening" of her health, the palace said on Friday. "We are reaching the point where a lung transplant will be necessary," Martin Holm, head of respiratory medicine at Oslo University Hospital, said.

Princess Mette-Marit told public broadcaster NRK that her illness had developed "faster than I'd hoped".

No decision has been taken yet on whether she will be placed on the transplant waiting list, Dr Holm said. The palace said her doctors had started the process towards an evaluation for lung transplant surgery.

In Norway, there are usually between 20 and 40 patients on the waiting list for a lung transplant and Princess Mette-Marit will not be given preferential treatment if she is placed on the list, local media reports.