Image source, Czech presidential press officeImage caption, A ballot box had to be brought to Mr Zeman so he could vote in the election due to his ill health
Czech President Milos Zeman has been taken to hospital amid political upheaval after a surprise opposition win in parliamentary elections.
The 77-year-old is a heavy smoker and former heavy drinker who uses a wheelchair and suffers from diabetes.
He was due to lead talks on forming a new government after Saturday's vote.
Prague's Central Military Hospital director said Mr Zeman was in intensive care for complications from a known condition.
"We know the diagnosis precisely, which allows us to target treatment," director Miroslav Zavoral said, but added that he would not give any further details per the president's request.
Mr Zeman's has previously said he is suffering from exhaustion and dehydration, after spending eight days in hospital last month.
But according to BBC Prague correspondent Rob Cameron, officials have not commented on claims by numerous sources that he is suffering from ascites, a build up of fluid in his abdomen most commonly associated with cirrhosis of the liver.
Mr Zeman was taken to hospital from the presidential chateau outside the capital Prague on Sunday morning, shortly after a meeting with Prime Minister Andrej Babis.
Footage broadcast by Czech media show staff holding up his head as he entered the hospital.
Prime Minister Babis and his populist ANO party had sought re-election on Saturday after four years in power. But they were beaten in the poll by the centre-right coalition Spolu (meaning Together), which took 27.8% of the vote compared to ANO's 27.1%.
Spolu has announced talks with the liberal Pirates/Mayors coalition known as PirStan to form a government. Together the two groups control 108 of the parliament's 200 seats.
However President Zeman said before the election he would pick the winner of the largest individual party, not coalition, to form the next government.
Because ANO took the most votes of any one party, this would be Prime Minister Babis – an ally of President Zeman's.
The president announced his plan to vote for the billionaire prime minister ahead of the poll. Due to his ill health however, a ballot box had to be brought to him so he could take part in Saturday's election.
According to Reuters news agency, the Czech constitution grants the lower house of the parliament the authority to appoint the prime minister if the presidential position is vacated.
A controversial figure, Mr Zeman is known for making divisive remarks and using strong language. In June he was sharply criticised for calling transgender people "disgusting".
Media caption, A video from 2017 asks whether Andrej Babis is the Czech Donald Trump