As authorities in Bangkok attempt to defend Thailand's capital from severe flooding, Channel 4 News Asia Correspondent John Sparks reports from north of the city where swathes of land are inundated.

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At least 283 people have been killed in Thailand by heavy monsoon rain, floods and mudslides since late July.

Save the Children estimates up to 500,000 young people may have been affected by the disaster.

Army chief Prayuth Chan-ocha told reporters that flood barriers in three vulnerable locations in Bangkok had almost been completed.

He said: "We talked about evacuation plans to help people living near the Chao Phraya river. If there's an emergency, we're ready to act.

"The worry now is that from today until 19 October there will be a high tide and the important thing is to push water out to the sea as fast as possible."

Much of the area is simply devastated. John Sparks

Channel 4 News Asia Correspondent John Sparks has flown over some of the affected areas: "Across the central planes of Bangkok it's simply too late.

"Housing estates, industrial estates simply inundated and we've seen hundreds of motorists stranded on isolated bits of highway. Much of the area is simply devastated."

The north, north east and central plains of Thailand have been worst hit and Bangkok, which is only two metres (6.5ft) above sea level, is in danger as water overflows from reservoirs in the north, swelling the Chao Phraya river.

Some outer areas of greater Bangkok have already flooded, but authorities hope the centre will be saved by existing defensive structures plus three new walls, which will help channel water to the east and west of the city into the sea.

Read more from John Sparks: Thailand's deadly monsoon season

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Run-off water from the north will arrive in the Bangkok area at the weekend at the same time as high tides. This may also coincide with storms and heavy rain.

Sanya Cheenimit, director of Bangkok's drainage and sewerage department, reported flooding in three eastern districts of Bangkok that were mainly farm areas.

"I want to reassure you that the flood situation in Bangkok is still under control. All the 50 districts of Bangkok have readied evacuation plans ... but for now, there's still no sign that we need to move people out."

Prime Minister Yingluck Shinawatra was also optimistic: "Bangkok we can say is safe, especially inner Bangkok, behind the embankments there won't be a problem. Outer Bangkok might have problems but the water won't be very high."

Despite the reassurances, residents have stocked up on bottled water and foodstuffs such as instant noodles.

More than 2 million people are estimated to have been affected by floods around the country and essential goods are in short supply in some areas because of disruption to road and rail traffic, with some main roads to the north cut off.