Bangkok: The health of Thailand's 88-year-old king Bhumibol Adulyadej has "not yet stabilised", the royal palace said on Wednesday night, amid unprecedented concern over the world's longest-serving monarch.

Earlier Thailand's military government urged people not to listen to rumours on social media about "situations", saying they should await official announcements.

The palace said the king's blood pressure had lowered again, his pulse rate had increased, there were high levels of acid in his blood and his liver function was abnormal.

The king was also on a ventilator.