Malawi's new president, Joyce Banda, has called for peace and unity as the nation mourns for her predecessor Bingu wa Mutharika, who died suddenly on Thursday.

Ms. Banda spoke on Saturday after being sworn in in the capital, Lilongwe, as Malawi's first female president.

“I call upon all Malawians to remain calm and to keep the peace during this time of bereavement. Further, I wish to direct that all national flags at public buildings be flown at half-staff, and that the Malawian broadcasting corporation and private media will play sombre music as we honor this mourning period, which is for 10 days. I would like to ask all Malawians that we mourn the father of this nation with dignity.”

President Banda served as vice president in Mr. Mutharika's government, but was expelled from the ruling political party in 2010. She formed an opposition party, but remained vice president. She succeeds Mr. Mutharika as mandated by the constitution. In her inaugural speech, she called for national unity, saying “there is no room for revenge.”

The United States sent condolences to the people of Malawi and the family of President Bingu wa Mutharika following his death. In a statement issued Saturday, National Security Council spokesman Tommy Vietor said the United States welcomes the announcement that Vice President Joyce Banda has been sworn in as president.

Mr. Mutharika died of a heart attack he suffered at home on Thursday, despite emergency treatment at a hospital in Lilongwe. The government delayed official confirmation of Mr. Mutharika's death until Saturday, giving rise to concerns that his supporters were maneuvering to install a member of the late president's ruling party as Malawi's new leader.