Tunisian President Bedji Cejd Essebsi is in hospital after he suffered a "severe health crisis," officials say.
They did not give more details. Mr Essebsi, 92, who is the oldest president in the world, was also treated in the hospital last week.
There were reports that the president had died.
Mr Chahed said in a Facebook post (in Arabic) that he had visited the president in a hospital.
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Earlier this year, he announced he would not stand the election expected in November, saying that someone younger should take responsibility.
After 23 years
Since then, Tunisia has won praise as the only democracy emerging from the revolutions of the so-called Arab Spring.
However, in recent years, the country has suffered attacks by Islamists and economic problems, with unemployment being a constant problem.
Earlier Thursday, there were two suicide bombings against the security forces in the capital, Tunisia. The Interior Ministry said one of them was targeting a police patrol on one of the city's main streets. One employee was killed and another injured with three civilians.
The second bomber – in another neighborhood – wounded four people in front of the gates of the National Guard.
It is not yet clear who is behind the attacks.