"It is still very early in this process but we have received a preliminary request from North Korean authorities, asking for our assistance."
Risely said a UN agency assessment team left the capital, Pyongyang, on Tuesday, headed for flood-hit areas.
Later on Tuesday, North Korea's official KCNA news agency said coal mining pits, power lines and substations had also been inundated or damaged.
Christopher Hill, US assistant secretary of state, said he would ask Washington to see what help could be offered.
"We are very concerned that this is a significant emergency crisis"
Paul Risely, World Food Programme Asia spokesperson
Speaking in Beijing, he said: "We've just been getting the press reports today on that flood, and in fact I asked if we could get some more information on it to see precisely what the situation is and to see what the appropriateness of assistance might be..
"I think we, like many other governments, will be looking into further details on it to see what can be done.
"We'll certainly be looking at it very seriously."
Some 63,300 families had been left homeless and nearly 6,000 Red Cross volunteers were carrying out evacuation and relief activities, according to the International Federation of Red Cross and Red Crescent Societies.
"The Red Cross rescue team in the capital city saved 14 people from swirling waters," the two organisations said.
Three big storms hit North Korea in 2006, and a newspaper close to Pyongyang reported that more than 800 people were killed or went missing in the resulting floods.
South Korea's unification ministry said it expected damage to be worse than last year.
A unification ministry official said the government was looking into possible flood aid for North Korea but had not received any request from Pyongyang.
The floods were not expected to spoil a planned leaders' summit between the two Koreas on August 28-30, he said.
State TV coverage
In an unusual move, the state's official TV station broadcast images of the damage, showing rain-swollen rivers and pedestrians walking through waist-deep water in flooded Pyongyang streets.
The broadcast was monitored in Seoul.
KCNA said at least 800 public buildings and more than 540 bridges had been washed away, while sections of railroad had been destroyed and thousands of homes ruined.
|Deforestation in the countryside has been |
blamed for the worsening floods
It also reported that scores of coal pits were submerged and many facilities destroyed.
More than 500 high-voltage power towers collapsed, five electric power substations of large capacity were inundated, and more than 10 transformers and other facilities severely damaged, KCNA added.
North Korea's infrastructure outside of showcase projects in Pyongyang is mostly a shambles. North Korea has few funds for building and still uses power and rail lines built during Japan's 1910-1945 colonial rule.
The flooding has hit most of the southern half of North Korea and includes the capital and some of its most productive agricultural regions. More rain is forecast for those areas over the next few days.