A sixth person has been confirmed killed by an explosion that flattened two New York City apartment buildings.

The body of an unidentified male was found in the rubble around 3.15am local time, a fire department spokesman said. A half hour earlier, a woman's body had been found.

A gas leak triggered the explosion yesterday morning on Park Avenue and 116th Street in East Harlem. The blast also injured more than 60 people. At least three of the injured were children.

The explosion shattered windows a block away, cast a plume of smoke over the skyline and sent people running into the streets.

Authorities say the fiery blast erupted about 9.30am local time, about 15 minutes after a neighbouring resident reported smelling gas.