United Nations officials say the capitals of Thailand and Cambodia are at risk as the worst flooding in modern times sweeps through the Mekong Basin.

Kirsten Mildren, spokeswoman for the U.N.'s humanitarian affairs agency, told VOA Tuesday that officials in Bangkok are taking urgent measures as the floodwaters bear down on the city.

Mildren said the waters are also continuing to rise in Cambodia, where Phnom Penh is threatened. Across the country 183 people have died since August and almost 100,000 hectares of paddy are damaged or destroyed.

Regionwide, she said at least 500 people are dead and millions are affected in Thailand, Cambodia, Laos and Vietnam.

In the northern Thailand city of Ayutthaya, resident Pathumwan Choichuichai told an Associated Press television crew he is very scared.

He said he has lost his home, his clothes and everything he owns in the flooding.

Mildren says the flooding is the result of an unusual combination of weather events, beginning with a series of typhoons that swept northwestward from the Philippines.

Her agency puts the death toll at 269 in Thailand, 183 in Cambodia, 30 in Laos and 18 in Vietnam, including 16 children.