BANGKOK » Thailand’s prime minister urged Bangkok residents to get ready to move their belongings to higher ground today as the country’s worst floods in half a century began seeping into the capital’s outer districts.

The warning came one day after the government opened several key floodgates in a risky move to let built-up water flow through the canals toward the sea. Authorities had said the canals could overflow, but it was not known to what degree.

An Associated Press team today saw water entering homes in Bangkok’s northern Lak Si district, along the capital’s main Prapa canal. The water rose to knee-level in some places but damage so far was minor and not affecting Bangkok’s main business district.

Prime Minister Yingluck Shinawatra told reporters the Prapa canal was a big concern as water there rose significantly overnight.

"I would like to ask people in all districts of Bangkok to get ready to move their belongings to higher ground as a precaution," Yingluck said, while also urging people "not to panic."

Gov. Sukhumbhand Paribatra said managing the Prapa canal was a "top priority" but vast pools of runoff draining through it from the north are expected to intensify.

Authorities have said immense networks of sandbagged barriers could deteriorate under pressure from the water, since they were not designed as dams. Yingluck said Wednesday there were no other options to slow the approaching water.

Excessive rains and storms have wasted a vast swath of Asia this year, killing 745 people — a quarter of them children — in Thailand, Cambodia, Vietnam, Laos and the Philippines, according to the United Nations.

Thailand’s government said today at least 342 deaths occurred here, mostly from drowning as floodwaters crept across this Southeast Asian nation since July. The floods have submerged land in about one-third of the country, leaving some towns under water more than six-feet-high (two-meters-high).

The threat of floods ruining treasured ancient palaces and chic boutiques along skyscraper-lined avenues has loomed large over this giant metropolis for weeks.

No major damage has occurred yet, and life is mostly normal in most of the capital. But many Bangkokians are girding for the worst.

"The water is coming, it’s inevitable," Oraphin Jungkasemsuk, a 40-year-old employee of Bangkok Bank’s headquarters, said Thursday. Its outer wall is protected by a six-foot-high (two-meter-high) wall of sandbags wrapped in thin plastic sheeting.

"They are fighting a massive pool of water. They cannot control it anymore," Oraphin said. "There are barriers, but it can come into the city from any direction, even up through the drains."

Economic analysts say the floods have cut Thailand’s 2011 GDP projections by as much as 2 percentage points. The latest damage estimate of $6 billion could double if floods swamp Bangkok.