The health of Thailand's King Bhumibol Adulyadej is “not stable”, palace officials have said.

As world's mass media noted, previously country's authorities informed the population about the health of the king only in cases if his condition improved.

As it was noted, the king's blood pressure had dropped as he was being prepared for haemodialysis, a procedure used to treat kidney failure. He was placed on a ventilator and medication helped return his pressure to normal levels, BBC reported.

King Bhumibol, 88, is the world's longest reigning monarch, but has spent much of the last year in hospital and is rarely seen in public.

King Bhumibol has been on the Thai throne since 1946. Residents of Thailand are now monitoring reports about his condition closely as many people consider that he is a national symbol of unification.