NASHVILLE, Tenn., May 4 (Reuters) - Flooding overwhelmed utilities in downtown Nashville on Tuesday, knocking out power and water service to thousands, after weekend storms were blamed for more than two dozen deaths.

“Power will be out for the next few days downtown due to water in underground vaults,” the city’s mayor, Karl Dean, said in a statement. He said 3,500 customers were without electricity.

The Cumberland River burst its banks and submerged several city blocks in Nashville’s downtown tourist district in sewage-tainted water.

Flooding that the U.S. Army Corps of Engineers called a “1,000-year event” also inundated sites such as the Grand Ole Opry entertainment and hotel complex, the football stadium, and one of two water plants serving the city of 626,000 people.

Mayor Dean asked residents to halve water usage, the city’s bus service was shut down, and schools were closed for a second day since more than a foot (30 cm) of rain fell over the weekend on parts of Tennessee, Mississippi and Kentucky.

Tennessee reported 19 storm-related deaths, including one from a tornado, Mississippi had six deaths and Kentucky two.

Thousands of people had to be evacuated, many by boat, and road closures were common.

Davidson County, which includes Nashville, postponed Tuesday’s scheduled election primary for two weeks because of the flooding.

Tennessee Governor Phil Bredesen declared disasters in 52 of the state’s 95 counties.

U.S. Senator Lamar Alexander of Tennessee said the region will get help from the federal government, dismissing suggestions that the Gulf oil spill would divert resources.

“The oil spill is being handled primarily by the oil industry. The federal people can’t do that. Federal folk usually get in early on something like floods. But it’s just saddening to me to see this situation,” he said.

The Cumberland River, which winds through Nashville, crested late on Monday about 12 feet (3.7 metres) above flood stage, but tributaries such as the Harpeth and Duck Rivers rose to record levels.

The Army Corps said it had to release water into the Cumberland from dams upstream to lower rain-swollen lakes. (Reporting by Pat Harris in Nashville and Andrew Stern in Chicago; Editing by Doina Chiacu)