Police in Tanzania have arrested four people on suspicion of spreading rumours on social media that President John Magufuli is ill.
The 61-year-old leader has not been seen in public for more than two weeks.
Prime Minister Kassim Majaliwa said last week that Mr Magufuli was "healthy and working hard".
But opposition politicians have said he's in a serious condition after contracting Covid-19 and had been flown abroad for treatment.
"To spread rumours that he's sick smacks of hate," Mr Majaliwa said on Friday, adding that he had spoken to him on the phone and that he had sent his greetings to the public.
On Monday, Vice-President Samia Suluhu Hassan told Tanzanians not to listen to rumours and urged them to remain united.
"It's quite normal for anybody to be afflicted by illness, to contract flu or a fever… this is the time for Tanzanians to be united through prayer," she said, without elaborating who she was talking about.
The four arrests were made in different parts of the country, with the first on Friday, says the BBC's Munira Hussein in Dar es Salaam.
Speculation about the president's health grows as each day passes, correspondents say.
Opposition leader Tundu Lissu told the BBC last week that his sources had told him Mr Magufuli was being treated in hospital for coronavirus in Kenya.
He said the president had suffered a cardiac arrest and was in a critical condition. But this claim has been denied by several Tanzanian officials.
Another Tanzanian politician told Associated Press, on condition of anonymity for fear of a backlash, that he had spoken to people close to the president who said he was seriously ill and in hospital.
Mr Magufuli has been accused of playing down the threat posed by the coronavirus and has been criticised for encouraging Tanzanians to rely on prayers, steam therapy and herbal remedies.