Thousands of Bangkok residents are moving out of the Thai capital as officials warn that flooding could get worse in the coming days.

Most of the city remained dry and most of its more than nine million residents were staying put to protect their homes. Still, uncertainty over Bangkok's fate and the start of a government-declared five-day holiday fuelled an exodus of thousands of people fearing the worst.

Tears welling in her eyes, Prime Minister Yingluck Shinawatra acknowledged her government could not control the approaching deluge.

"What we're doing today is resisting the force of nature," Yingluck told reporters. She said the water bearing down on Bangkok was so massive that "we cannot resist all of it."

By Thursday, flooding had inundated seven of Bangkok's 50 districts, most on the northern outskirts. There, roads have turned into rivers and homes and businesses are swamped.

The local transportation authority had to divert some buses because of flooding, and on a flooded key east-west artery police were turning back small cars, telling them the road had become impassable.

Bangkok's governor, Sukhumbhand Paribatra, told the Bangkok Post that officials did not believe that all the districts in the capital city would be flooded. He said officials were doing what they could to protect the city from the rising waters and were closely monitoring the water levels in several at-risk neighbourhoods.

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Thai residents wait for a vehicle to evacuate from a flooded area in Bangkok. ((Sakchai Lalit/Associated Press))

"Today marks the start of a five-day special disaster holiday announced by the government to help people deal with the crisis — and many are taking advantage of it," Bangkok-based reporter Michael McAuliffe said Thursday.

McAuliffe said there were long lines at train and bus stations. Large crowds were also reported at the city's main international gateway, Suvarnabhumi airport, which remained open.

"Highways going south — away from the floods  — are jammed with cars carrying people on their way to the nearby resort communities of Pattaya and Hua Hin, which have both sold out of hotel rooms," McAuliffe said.

The city's second-largest airport, which is also home to the Flood Relief Operations Command, was swamped earlier this week when floodwaters breached barriers.

In Bangkok, many residents were staying put and preparing for the worst. Some people built concrete walls to protect their shops and homes. Many residents fortified vulnerable areas of their houses with bricks, gypsum board and plastic sheets. Walls of sandbags or cinderblocks covered the entrances of many buildings.

Residents stocking up on food and other necessities have emptied supermarket shelves, and stores have posted notices that flooding was disrupting supply chains and preventing them from restocking certain items.

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People are evacuated on a truck from a flooded area in Bangkok, where residents are bracing for more flooding. ((Sukree Sukplang/Reuters) )

Residents living near Mahasawat Canal in western Bangkok evacuated on Wednesday after a rapid overnight rise in water.

"I decided to leave because the water came in very fast," said Jong Sonthimen, a 57-year-old factory cleaner. A boat carried her and two plastic garbage bags with her belongings to a Buddhist temple, where pickup trucks waited to take residents to a safer area.

The government was also taking action, setting up emergency shelters in Bangkok and surrounding provinces, with schools and other buildings being readied to accommodate people fleeing floods.

The military was also involved in flood preparation, with armed forces members ready to provide assistance if needed during an evacuation, the Post reported.

Key floodgates were opened in Bangkok to help drain run-off through urban canals to the sea, but rising tides in the Gulf of Thailand this weekend could slow the process and flood the city.

Canadian officials are advising against non-essential travel to Bangkok and other flood-affected areas.

"These conditions are causing travel disruptions and have interrupted other essential services, such as the power supply and communications in some affected areas," the Department of Foreign Affairs says in a travel advisory.

"Further disruptions to essential services, as well as shortages of drinking water and some food items may occur, including within the Bangkok Metropolitan Area."

The Canadian warning doesn't include people passing through the city's busy Suvarnabhumi airport, an international hub that is still operating.

In a news release, the World Health Organization cited Ministry of Interior figures from last week that said officials have set up 912 temporary shelters in 11 provinces, though those figures likely expanded as the situation in Bangkok and other areas deteriorated.

The floods, which have swept through a large swath of the country have killed more than 373 people since July and caused billions of dollars in damage. Thai officials say 26 provinces are affected by the floodwaters.

With files from The Associated Press