BANGKOK Rescue workers reinforced make-shift walls and sand-bags around Bangkok on Saturday as the worst floods in half-a-century threatened Thailand's low-lying capital after swamping entire provinces in the north.
Prime Minister Yingluck Shinawatra sought to reassure Bangkok's 12 million people they would largely escape floods that have swept over a third of Thailand since July, killing at least 297 people, causing about $3 billion in damage and turning villages and industrial parks into lakes.
The north, northeast and center of Thailand have been worst hit and Bangkok -- much of it only two metres (6.5 ft) above sea level -- is at risk as water overflows from reservoirs in the north, swelling the Chao Phraya river that winds through the densely populated city.
Yingluck said Bangkok is well fortified after authorities raised embankments at the three outer areas.
Despite official assurances, residents stocked up on bottled water, instant noodles, rice and canned goods, emptying shelves in some major markets. Many parked their cars in elevated garages, or piled sand-bags in front of shop-houses and homes.
"If we are not prepared for the floods, it is hard to imagine what will happen if the government cannot help us in time," said Sompong Pinmaninsab, a bank worker in Ta Prachan, a Bangkok district known for its markets next to the Chao Phraya river. "Anything can happen."
Water released from several dams should reduce the chance of floods, Yingluck said, as northern run-off water approaches Bangkok over the weekend, coinciding with high estuary tides that hamper the flow of water into the sea.
"We will protect strategic areas and the heart of the economy such as industrial zones, the central part of all provinces and the Thai capital as well as Suvarnabhumi Airport, industrial estates and evacuation centres," she said, referring to Bangkok's main international airport.
The United States dispatched a C-130 military transport aircraft with 1,000 sand-bags and 10 Marines in a humanitarian mission, U.S. embassy spokesman Walter Braunohler said in a statement.
Twenty-five of Thailand's 77 provinces are flooded with 4 million acres (1.62 million hectares) of farmland under water -- about 16 times the size of Hong Kong. Nearly 800,000 homes have been destroyed or damaged. Thousands of people huddled in evacuation centres.
Ayutthaya, Pathum Thani and Nakhon Sawan provinces north of Bangkok have been devastated. Floods have swallowed up homes, swamped streets and destroyed industrial parks, partly a result of desperate measures to shield the capital.
To protect the Bangkok, authorities have reinforced its last Defenses -- a 4 km (2.5-mile) flood barrier along a canal and a sluice gate in Pathum Thani province north of the city, where offices, shops and restaurants have been submerged in chest-high water and many residents now get around in boats.
Bangkok, known for historic temples, bustling markets and raucous nightlife, is on edge amid bickering between the government and the city's governor. The two are on either side of a political divide that sparked violent protests last year.
Bangkok, the business heart of Thailand, accounts for 41 percent of its economy. In comparison, the badly flooded central region accounts for 8 percent of the economy, Southeast Asia's second largest.
Parts of the central province of Ayutthaya, home to an ancient Siamese capital founded in the 14th century, are deep under water, forcing at least three big industrial estates to shut temporarily. Several spectacular monuments and temples have been flooded for days.
Cresting water breached the flood-walls at the Bang Pa-In industrial estate on Saturday in Ayutthaya, about 60 km (37 miles) north of Bangkok, forcing authorities to evacuate plant workers, Defense Minister Yutthasak Sasiprapa told Reuters.
"We tried hard but could not stop it," Yutthasak said.
There are 84 companies in the estate including foreign firms from Japan, Taiwan and Germany along with Thai-Japanese and Thai-U.S. joint ventures, according to information on its website.
On Friday, Japanese automaker Honda Motor Co Ltd shut its Ayutthaya plant that accounts for 4.7 percent of its global output. It will stay closed until October 21.
Thailand is Southeast Asia's biggest auto-manufacturing hub with most factories located in the east, which has been little affected by the flooding. But their operations could still suffer because car parts firms have been hit.
Thai media said floods had almost completely isolated Samkok, a district in Pathum Thani province, making it inaccessible by car and stranding locals.
(Additional reporting by Jutarat Skulpichetrat and Pracha Hariraksapitak. Writing by Jason Szep; Editing by Sanjeev Miglani)