Police in Tanzania has arrested four people on suspicion of spreading rumours on social media that President John Magufuli is ill.
He has not been seen in public for more than two weeks.
Opposition politicians have said he's in a serious condition after contracting Covid-19 and has been flown abroad for treatment.
Government officials have denied this.
Tanzania's Vice-President Samia Suluhu Hassan said the president was working hard.
She advised people not to listen to rumours and urged Tanzanians to remain united.
Mr Magufuli has been accused of playing down the threat posed by coronavirus and has been criticized for encouraging Tanzanian to rely on prayers, steam therapy and herbal remedies.