Denmark’s Queen Margrethe II, whose half-century reign makes her Europe’s longest-serving monarch, has undergone "extensive back surgery" and the condition of the monarch "is good and stable under the circumstances," the palace said.

The 82-year-old queen will remain in the hospital "for some time to come," and that will be followed by a period of convalescence and rehabilitation, according to the royal household.

Several official engagements have either been postponed, canceled or are being handled by other members of the royal family.

DANISH QUEEN STANDS BY DECISION TO STRIP ROYAL TITLES FROM GRANDKIDS

The queen's oldest son, heir to the throne Crown Prince Frederik, and his wife, Crown Princess Mary, will step in in, as well as the queen’s sister, Princess Benedikte, the palace said Wednesday hours after the surgery.