Malawians are still waiting for official word about President Bingu wa Mutharika, amid multiple reports that the president has died.
Mr. Mutharika was rushed to a hospital in the capital, Lilongwe, on Thursday after falling ill at his home. State media said he was flown to South Africa but have given no further information.
Medical and government sources, speaking on condition of anonymity, say the 78-year-old president died of a heart attack.
At a news conference Friday, Vice President Joyce Banda said she is trying to learn more about the situation, adding that she and other Malawians are, in her words, "in the dark."
Malawi's former president, Bakili Muluzi, urged officials on Friday to release information about Mr. Mutharika.
"The present scenario where the government is almost silent on the health status of the president is very unfortunate, and ought not to continue," said Muluzi. "It is the constitutional duty and indeed good practice of the government to inform its citizens and the world community timely, accurate and transparent information about the particulars of the ongoing treatment and health condition of their sick president."
He also called on politicians to respect the constitution, which states Vice President Banda should take power if the president is incapacitated.
"My humble appeal to all politicians involved both in government and those in opposition is that they should put the interest of the country ahead, as we anxiously await to hear from the doctors attending upon our president," he said.
Mr. Mutharika was elected president of Malawi in 2004 and won a second term in 2009.
He was credited with improving food security in Malawi and, at one time, making his country a political and economic model for other African countries.
But in more recent years, the economy has stumbled and unemployment has been high. Critics of the president say he had become increasingly autocratic. Nineteen people were killed last July in anti-government protests.
An economist by education, Mr. Mutharika was a World Bank official and served as a civil servant in Malawi. He was appointed minister of economic planning and development in 2002 and then-President Muluzi nominated him as his successor.
He later broke away from Mr. Muluzi and formed the Democratic Progressive Party, which has the majority in parliament.
Some information for this report was provided by AFP and AP.