Rising floodwaters seeped into Bangkok's Don Muang airport Tuesday, halting flights and prompting authorities to begin moving people out of a major evacuation center at the facility.

Bangkok's main international airport, southeast of the city, was not affected. But Don Muang, located near flooded districts in the city's northern suburbs, is the site of Thailand's main depot for flying emergency supplies to inundated areas in northern Thailand.

As floodwaters lapped at the airport's runways and impeded access from outside, authorities advised thousands of people who have been living in one of the airport terminals to begin moving to another evacuation center far to the south.

Late Monday, Bangkok's governor warned residents along the banks of the Chao Phraya River to be on full alert as rainwater flooding vast areas of central Thailand bear down on the city. He said the worst is expected this weekend, when the water could spill over the levees along the river's banks.

Two airlines operating domestic flights out of Don Muang announced they are shutting down operations there, and a railway officer said rising waters in the western suburbs could force a halt to train traffic to the country's south.

The officer said officials are monitoring the situation day to day.

Several industrial parks north of Bangkok have already been flooded, delivering a huge blow to Thailand's manufacturing base. Shopkeepers and businessmen say they too will suffer if the trains are forced to shut down.

The latest U.N. figures show flooding has killed 356 people in Thailand and almost 800 people across Southeast Asia. The U.N. says almost 2.5 million people are affected in Thailand and more than 8 million across the region.

The organization says widespread damage to rice paddies could lead to serious food shortages. it also warns that hundreds of thousands of people are at risk of water-borne diseases.