The damage from monsoon flooding in Sri Lanka over the last six weeks is estimated at $600 million, a government minister said Sunday amid a slow response to an international appeal for help.

Disaster Management Minister Mahinda Amaraweera said the government would spend 33 billion rupees ($300 million) to carry out urgent repairs to 50,000 homes damaged by the flooding.

"The total flood damage bill is estimated at twice as much," Amaraweera told AFP. "The rice crop damage alone is about 13 billion rupees."

The unusually heavy monsoon rains left at least 64 people dead and drove more than one million people out of their homes.

Most of them have returned as rains subsided, but 130,000 people still remain in state-run welfare camps, the disaster management centre said Sunday.

The United Nations issued an appeal for $51 million to address immediate needs after the first round of flooding, but received only about 20 percent.

It plans a fresh appeal after the second wave of floods hit the northern, central and eastern parts of the island.