Thailand's prime minister remained optimistic Sunday that the capital would be spared any additional destruction from the worst flooding in decades.

Yingluck Shinawatra asked her compatriots to have confidence in the government's ability to handle the flooding, even as some dikes in Bangkok overflowed Sunday.

The city's northern districts were submerged Saturday, as well as one-third of the countryside. High tides pushing water from the gulf of Thailand into the city's Chao Phraya river basin are expected to last into Monday.

Buildings in the city center are surrounded by sandbags, but ankle-high water from the river has reached the area around Bangkok's iconic Grand Palace and other tourist attractions.

Tens of thousands of residents have fled the area on bamboo rafts, vans, army trucks or on foot, heading for higher ground in the south. Many have flown out of the city.

The flooding that began in July – the country's worst in 50 years – has already claimed more than 380 lives. The material losses are yet to be determined.

Prime Minister Yingluck said in her weekly radio address Saturday that the waters will start receding this week. The water has already receded in the central region of the country.

The U.S. Defense Department says Thailand had asked a U.S. destroyer to extend its stay at a main port to allow two U.S. helicopters to survey the flood.