Malawi's vice president, Joyce Banda, was sworn in as president Saturday in the capital, Lilongwe, following confirmation that President Bingu wa Mutharika died suddenly on Thursday.

Ms. Banda, who is Malawi's first female president, was expelled from the ruling party in 2010. But she kept the vice presidency and now ascends to the presidency by constitutional mandate. In her inaugural speech Saturday she called for unity, saying “there is no room for revenge.”

She said she had a good meeting with the cabinet earlier in the day and called the discussion a starting point for healing the wounds of the nation. And she thanked all Malawians for respecting a peaceful transition to the presidency.

Though President Mutharika had his fatal heart attack on Thursday, the government delayed official confirmation of the death until Saturday, while rumor and unconfirmed reports circulated. The delay gave rise to concerns that the late president's supporters were maneuvering to install a member of the ruling party as president.

President Banda has announced that the nation will observe 10 days of mourning, during which flags will fly at half-staff and broadcasters are asked to play somber music.

Mr. Mutharika died of a heart attack he suffered at home on Thursday, despite emergency treatment at a hospital in the capital, Lilongwe.

He was elected president of Malawi in 2004 and won a second term in 2009. Once hailed as a leader in improving food security in African countries, he fell out of favor after suppressing anti-government protests in July. Nineteen people died in the violence.

An economist by education, Mr. Mutharika was a World Bank official before working his way up through the ranks of Malawi's government. He formed the Democratic Progressive Party, which now has majority control over parliament.