Thailand's royal palace has released a vaguely worded health report on the country's 88-year-old king, the world's longest reigning monarch who has been ailing for years, describing what appears to be a new bout of lung infection and occasional fever with rapid breathing.

The statement issued late Sunday raised concern about the frail health of King Bhumibol Adulyadej, who has spent most of the past six years living in a Bangkok hospital.

The Royal Household Bureau statement said the king had battled a fever for the past two weeks and that tests found "an infection in the lower part of the lungs" and an infection in his blood as well as inflammation in his right knee joint.

The king was given oxygen, intravenous antibiotics and other medication, the statement said, adding that "currently, the king's fever has eased but his breathing is occasionally faster than normal, while his pulse and blood pressure are normal."

The statement did not make clear if the lung infection was gone.

Bhumibol, who took the throne in 1946, has faded from public life in recent years due to ill health.

The king is deeply revered in Thailand. He is a constitutional monarch with no formal political role but has been regarded as a stabilizing figure for Thailand, which has experienced political turmoil in recent years. Many regard him as a father figure and his Dec. 5 birthday is celebrated as Father's Day in Thailand.

Worries about the king's health and succession have contributed to the country's political instability but little public discussion has been allowed. The heir apparent, Crown Prince Vajiralongkorn, does not command the same respect and affection as the king.

The Associated Press