Medical sources say Malawian President Bingu wa Mutharika has died after suffering a heart attack, but there has been no official announcement of his death.

Diplomatic sources say the 78-year-old president collapsed after falling ill at his home in the capital, Lilongwe, on Thursday.

He was rushed to a local hospital, where sources say he died. However, the Malawian government has yet to issue a statement on the president's condition.

Malawi's former president, Bakili Muluzi, urged officials on Friday to release information about Mr. Mutharika.

He also said if the president is dead, the constitution stipulates that the vice president, Joyce Banda, must take power until new elections are held.

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 Bakili Muluzi nominated him as his successor. Mr. Mutharika was the head of the ruling Democratic Progressive Party, which has the majority in parliament.