So many rats have drowned in Cambodia's worst flooding in over a decade that the cross-border trade in the rodent's meat has plummeted, Prime Minister Hun Sen said Wednesday.

"Each year 17 tonnes (about 37,000 pounds) of rats are exported to Vietnam. This year there is a shortage of rats for export because the rats have died in the floods," he said, citing reports from officials at the southern Chrey Thom border checkpoint.

While there are no clear figures on the scale of the industry, rat meat is considered a cheap and tasty treat in Vietnam and the country is a keen importer of live rats from Cambodian villages along the border.

Ros Sothea, chief of Chrey Thom border checkpoint, told AFP he had no statistics on the impact of this year's floods on the trade but he had noticed very few rats were being sold to Vietnam.

"Almost no rats are being exported to Vietnam because the floods have killed them," he said. "Last year, a lot of rats were exported," he said.

Cambodia's deadliest floods since 2000, triggered by heavy rains, have killed at least 247 people and destroyed nearly one tenth of the nation's rice paddy.