King of Thailand dead: World's longest reigning monarch King Bhumibol Adulyadej dies aged 88

Official mourning is expected to last up to a year

King Bhumibol Adulyadej attends a ceremony at the Grand Palace in Bangkok in 2010 (Reuters)

The world's longest-reigning monarch, King Bhumibol Adulyadej of Thailand, has died aged 88, the palace has confirmed.

The palace said the King passed away peacefully on Thursday at Bangkok's Siriraj Hospital after a 70-year reign.

Bhumibol Adulyadej became king in 1946 and was revered in Thailand as a demigod. He anchored the South-east Asian country through violent upheavals at home and communist revolutions next door, as well as a period of rapid development.

Parliament met in a special session later on Thursday after a meeting of the cabinet.

Prime Minister Prayuth Chan-o-cha announced before the session that King Bhumibol's son and heir apparent, the 63-year old Crown Prince Maha Vajiralongkorn would be the new monarch in accordance with the constitution.

However, the parliamentary meeting ended without inviting a successor to ascend to the throne.

Mr Prayuth said that the Crown Prince had asked for time to mourn with the Thai people. “Let us wait for the right time,” Mr Prayuth said, before adding that: "When the right time comes, the Crown Prince confirmed that he has realised his duty and will continue to perform his duty as the heir to the throne“.

Anxiety about the King's health and the succession has formed the backdrop to over a decade of political upheaval in Thailand that has included two coups. King Bhumibol was seen as a force for unity - particularly given the length of time he sat on the throne - and there have long been concerns that without him the country's divisions could worsen.

That appears unlikely under the military government of Prime Minister Prayuth, who has kept a tight grip on power since toppling an elected government in 2014. That followed a previous army-staged coup in 2006, with a number of other attempted or successful

King Bhumibol was viewed by many in the majority Buddhist nation as a "bodhisattva", or holy being who delays entering nirvana to aid the human race, with junta leaders and Prime Ministers all showing due deference.

Hundreds of tearful Thais have journeyed to the hospital since King Bhumibol's deteriorating health was first announced by the palace on Sunday. Wearing pink and yellow shirts in the King's honour, many in the crowd have sat in the hospital courtyard, positioned to look up toward the building where the King has been confined. Every now and they shout “Long live the king,” with some wiping away tears.

Many more broke into tears after the King's death was announced. “I feel so saddened by this news. He has given so many things to the country,” Apinut Jaroonpipatkul, a 25-year-old medical student told Reuters.

Parichart Kaewsin, 35, who works in a bank, stood at the edge of the hospital garden, gazing up at the top floor of the building where the king was treated.

“I knew he was sick but I still can't believe this day has come,” she said, choking back tears.

“That's why I came here - to hear for myself.” She told Reuters it was like a member of her family has died, she said. “He was like our dad.”

The once-vigorous King had withdrawn from public life over the last decade due to his ill health. He lived at a Bangkok hospital and had been notably silent about the political upheaval that has shaken Thailand in recent years.

His apparent successor Prince Vajiralongkorn has yet to command the respect and adoration that his father drew after a lifetime on the throne.

He has kept a lower profile than King Bhumibol for most of his life but in the past two years took on more of the public duties the king was no longer able to perform. The prince divorced his third wife in 2014.

Thailand's strict lese-majeste laws has left little room for public discussion about the succession. It has been so long since Thailand has had a succession, there is no modern precedent.

Mr Prayuth said that the government will observe one year of mourning and flags will fly at half-mast for 30 days. No government events will be held for 30 days, he said.

The Prince's coronation will not take place until a mourning period is over. When the King's sister died in 2008, a 100-day mourning period was declared. She was cremated 10 months after her death.

King Bhumibol also garnered respect from around the world, with the US seeing him as a crucial ally as communist revolutions erupted around the region.

There were a number of tributes to the King from leaders all over the world on Thursday.

US president Barack Obama offered his condolences to Thailand. He said the King leaves behind a legacy of care for the Thai people that future generations will cherish.

He said King Bhumibol was a tireless champion of his country's development and showed an “unflagging devotion” to improving the standard of living for the Thai people.

Mr Obama said the king was a close friend of the United States and valued partner of many US presidents.

Malaysian PM Najib Razak also offered his heartfelt condolences to the Thai royal family and the people of Thailand.

“King Bhumibol was a towering presence whose contribution to Thailand, and the rest of the region, is beyond words. We join the Thai people in mourning his loss,” he said..

While, Japan's Prime Minister Shinzo Abe said he was in “deep sorrow” at the death and remembered King Bhumibol as a "gentle person".