Malawi's government has confirmed, after more than a day of uncertainty over who was running the impoverished south African country, that President Bingu wa Mutharika is dead and his vice-president has been sworn in to take his place.

Bingu wa Mutharika died of cardiac arrest on Thursday. (Jon Black/Associated Press)

In a statement released Saturday, Malawi's Chief Secretary Bright Msaka said 78-year-old Mutharika died on Thursday.

"His Excellency the President Ngwazi Professor Bingu wa Mutharika, who suffered cardiac arrest at the State House in Lilongwe at about 11:15 a.m. on Thursday April 5, 2012, was confirmed dead on the same day upon arrival at the One Military Hospital in Pretoria, South Africa," Msaka said in the statement.

Vice-President Joyce Banda on Saturday moved to take charge of the country by holding a news conference at which the cabinet ministers appeared and by calling for 10 days of national mourning.

"I wish to direct that all national flags at public buildings be flown at half mast and that the Malawi Broadcasting Corporation and private media of goodwill will play sombre music," she said at her official Area 12 residence in the capital, Lilongwe.

Banda will hold post at least until next election

Banda, 61, is now the first female head of state in southern Africa. Under the constitution, the vice-president should take over to complete Mutharika's term, due to end in early 2014.

Joyce Banda was Malawi's foreign affairs minister from 2006 to 2009. (Thierry Roge/Reuters)

Banda had clashed with Mutharika over proposed succession rules for the presidency and was expelled from his party last year, but held on to the vice-presidency.

The delay in announcing Mutharika's death had led to speculation politicians were still squabbling over succession.

Mutharika had favoured his brother, Foreign Affairs Minister Peter Arthur Mutharika, over Banda, appointing him acting president when he travelled. Friday, Mutharika's party had named Peter Arthur Mutharika its acting head, though the party did not then confirm Mutharika's death.

Mutharika was a former World Bank official once heralded for his stewardship of one of the world's poorest countries. In recent years, he had been accused of trampling on democratic rights.

Mutharika first came to power in a 2004 election, and was overwhelmingly re-elected five years later.

During his first term, Mutharika persisted with a program to help farmers buy fertilizer even though Western donor nations and agencies said subsidies should be avoided in a free market. His subsidies were credited with boosting Malawi's economy.

In more recent years, the economy has stumbled, with shortages of fuel and foreign currency and high unemployment.

Anti-government demonstrations across Malawi last year were met with an unprecedented security crackdown that resulted in at least 19 deaths.

Malawi's relations with foreign donors have been strained by accusations Mutharika is authoritarian and responsible for human rights abuses. Last month, a U.S. aid agency that rewards good governance suspended $350 million worth of assistance to Malawi.