Samura Kamara, outgoing President Ernest Bai Koroma's pick as successor, will face off against Julius Maada Bio, who lost to Koroma in 2012.
Bio took 43.3 percent to Kamara's 42.7 percent in the first round of voting last week, according to results released late Tuesday. The two emerged from a crowded field of 16 candidates.
The winner of the March 27 runoff will be tasked with helping the country continue to rebuild after the devastating 2014-2016 Ebola epidemic.
The capital also was battered by a deadly mudslide in August that claimed some 1,000 lives.
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