The president of Myanmar Htin Kyaw has resigned, his office has announced.
No reason was given, but there have been growing concerns in recent months about the 71-year-old's health after he appeared frail at official functions.
Htin Kyaw was sworn in as president in 2016 after landmark elections which ended decades of military leadership.
But he was essentially a ceremonial leader, with long-time opposition leader Aung San Suu Kyi acting as de facto president.
The statement posted on the presidency's Facebook page said Htin Kyaw wanted to "take a rest".
Vice-President Myint Swe, a former general, would act as president until a new president is chosen within seven days, it said.
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Ms Suu Kyi, who was jailed for years under the military junta, was banned from taking the top job.
A clause in the constitution – widely seen as being deliberately designed to keep her from office – states that no-one with children of another nationality can be president.
She had two children with her late British husband.
Htin Kyaw was her childhood friend, long-time advisor and some time driver. He was widely seen as quiet and dependable, and someone she could trust entirely.
Dogged by Rakhine crisis
Ms Suu Kyi's National League for Democracy had a landslide win in elections held in November 2015.
But the leadership has been dogged by issues since it took power, most prominently the crisis in Rakhine state.
Tens of thousands of stateless Rohingya migrants have fled amid a military crackdown sparked by deadly attacks on police stations.
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The government said it was targeting militants, but the scale of the operation has led to accusations that it could amount to genocide.
It has also seen Ms Suu Kyi's global popularity plummet, and she has found herself increasingly isolated by her former international allies.