The presidential palace, Haiti's grandest building, was substantially destroyed and its incumbent, Rene Preval, described the scene in his capital as "unimaginable".
His prime minister, Jean-Max Bellerive, said the government believed the death toll in the city of two million people was "well over 100,000" while Youri Latortue, a senior senator, said it could be 500,000.
Both admitted they had no way of knowing but aid workers on the scene reported widespread destruction and suffering as severely injured people lay in the streets, unable to get medical assistance.