Ernest Bai Koroma said entire communities had been wiped out and that the "devastation was overwhelming us".
Nearly 400 people have been killed and hundreds more are missing after muddy rubble swept through the Regent area near the capital, Freetown, on Monday.
A mass burial of victims is planned to free up space in mortuaries.
Dozens more bodies were discovered on Tuesday, as rescue efforts to recover people from destroyed houses in the area continue.
