The agency said downpours earlier this month "caused huge material losses to the [country], creating unprecedented difficulties in people's living and economic construction".
KCNA said the homes of at least 240,000 families were totally or partially destroyed or inundated, leaving at least 100,000 people totally homeless and some 900,000 others flood-stricken.
Some 200,000 hectares of cropland was submerged, buried under silt or washed away just before the harvest, the agency said.
North Korea faced a food shortfall this year of one million tonnes, or 20 per cent of its needs, even before the floods. It relied on international aid to help cover the shortfall.
KCNA said more than 8,000 public buildings, schools, health facilities and nurseries were totally or partly destroyed, along with more than 1,000 major production facilities since as mine complexes and factories.
It reported "serious damage to all sectors of the national economy."
On Friday, South Korea said it is giving an extra $40m in aid to flood-hit North Korea after Pyongyang requested help with reconstruction.
"North Korea is having difficulties recovering from the floods because of the shortage of construction equipment and material," Lee Jae-joung, South Korea's unification minister, said.
"It badly needs such material and equipment."
The aid – which comes in addition to an earlier $7.5m emergency relief package - includes cement, reinforcing rods, trucks, construction equipment and fuel, Lee said.
The aid is to help rebuild houses and roads and delivery is to start in mid-September, he said.
He said that transporting the supplies would cost an additional $10.6m.
The floods have led to the postponement of a landmark summit between the leaders of the two Koreas from end August to early October.