(CNN)Tanzania's President John Magufuli has died at a hospital in Dar es Salaam, the country's vice president announced in a televised address on Wednesday. He was 61. "President John Magufuli died of a heart ailment that he has battled for over 10 years," Samia Suluhu Hassan said. She added that the president had been receiving treatment at Mzena hospital since Sunday, and announced 14 days of national mourning. Hassan is now the acting president of Tanzania. While a date for her swearing-in has not yet been announced, she will be Tanzania's first female president.