The 81-year-old king of Thailand has been admitted to hospital suffering from a fever.
Doctors said King Bhumibol Adulyadej, the world’s longest-serving monarch, had shown signs of fatigue and was being treated with antibiotics.
King Bhumibol is deeply revered by most Thais and his health is a matter of public anxiety.
Prime Minister Abhisit Vejjajiva told reporters there was “nothing to be concerned about”.
People have gathered at the hospital to offer prayers and convey their good wishes.
A statement from Thailand’s royal household said King Bhumibol was taken to the Siriraj hospital in Bangkok on Saturday night.
The Royal Household Bureau said the king was suffering from a fever, fatigue and loss of appetite. He is being treated with intravenous drips and antibiotics.