Malawi's President Joyce Banda says this week's general elections have been marred by "serious irregularities" that include vote rigging, ballot tampering and people voting multiple times.
In a Thursday statement, she urged the election commission to begin an "immediate manual audit" of the voting process.
Malawians went to the polls on Tuesday to choose a new president, members of parliament and local government officials.
But long delays and ballot problems prompted election officials to extend voting into Wednesday and Thursday in some areas.
The problems and delays angered some voters, who blocked roads in the main city of Blantyre on Tuesday and set fires at polling stations.
Election commission chief Maxon Mbendera discounted the president's accusations and said election officials are already using manual vote counting. He urged Malawians to wait for the official results before making complaints about the vote outcome.
The head of the EU Election Observers Mission in Malawi, Veronique De Keyser, also cited incidents in which polling stations lacked essential materials, which resulted in delays. But she said election commission officials acted impartially throughout the process
President Banda is facing stiff challenges from some of her 11 contenders, in the first democratic test of her rule.
She rose to power two years ago when her predecessor, Bingu wa Mutharika, suddenly died in office. At the time, she was serving as vice president.
Early, unofficial reports indicate she is trailing challenger Peter Mutharika, the brother of the late president.