Malawi's President Peter Mutharika has been sworn in for a second five-year term after an election in which top opposition parties alleged irregularities.

The 78-year-old Mutharika began his acceptance speech by declaring "I am not dead!" to address persistent rumors ahead of the vote. He added that "it is time to move on and develop the country."

He narrowly won re-election with 38% of the votes in last week's polls, while main opposition leader Lazarus Chakwera received 35%.

Shortly after the swearing-in, police were seen firing tear gas outside the headquarters of Chakwera's Malawi Congress Party. Neither the party nor police immediately commented.

Mutharika's former deputy Saulos Chilima finished third in the election and on Monday went to court to petition for the nullification of the vote, alleging serious anomalies.