The US Coast Guard late Friday closed a section of the swollen Missouri River to recreational vessels because of high water levels and flooding.

"This measure will be in effect until the water levels decrease in order to ensure the safety of the boating public," Captain Steve Hudson, Coast Guard's commanding officer for the region, said in a statement.

The 182-mile (293-kilometer) section begins in Yankton, South Dakota and goes southward. Commercial vessels have voluntarily ceased operations there, the Coast Guard said.

Above-normal snowpack and torrential rains in recent weeks have raised flooding fears along the Missouri, one of the world's longest rivers at 2,340 miles (3,766 kilometers).

The US Army Corps of Engineers reported Friday that reservoirs are at capacity, requiring the release of large amounts of water from all dams.

"There's flooding that's going on up river. There's a lot of water and debris coming down the river. It's going to be dangerous for recreational vessels," Chief Warrant Officer Ancil Brown said.

Significant flooding in cities, towns and agricultural land was expected in the Great Plains states of North and South Dakota, according to the Army Corps. Several thousand residents have evacuated in recent days.

South Dakota has issued an emergency declaration "in anticipation of flooding in areas along the river," the Coast Guard said in its statement.

The Coast Guard has staged a disaster "response team" in the area to help any rescue missions that may occur.