NAIROBI, Kenya — President John Magufuli of Tanzania, a populist leader who played down the seriousness of the coronavirus pandemic and steered his country away from democratic ideals, died on Wednesdayin the port city of Dar es Salaam. He was 61.

Vice President Samia Suluhu Hassan said in a brief televised address that Mr. Magufuli had died of heart complications while being treated at Mzena Hospital. The announcement followed more than a week of intense speculation that Mr. Magufuli was critically ill with Covid-19 — reports that senior government officials had repeatedly denied.