UPDATE 6-Tornadoes, Storms Rip US South, at Least 259 Dead

* Damage over several states, Alabama worst with 162 dead

* Mile-wide tornado tears through university town

* Alabama nuclear power plant shut after storms

* White House says Obama to visit Alabama on Friday

(Updates toll, adds quote, comment on insurance costs, Obama)

By Verna Gates

TUSCALOOSA, Ala. (Reuters) - Tornadoes and violent storms ripped through seven southern U.S. states, killing at least 259 people in the country's deadliest series of twisters in nearly four decades.

The clusters of powerful tornadoes -- more than 160 in total -- combined with storms to cut a swath of destruction heading from west to east over several days. In some areas, whole neighborhoods were flattened, cars flipped over and trees and power lines felled, leaving mounds of tangled wreckage.

At least 162 people died in Alabama, the worst-hit state which suffered "massive destruction of property," Governor Robert Bentley said Thursday.

The mile-wide monster twister that Wednesday tore through the town of Tuscaloosa, home to the University of Alabama, may have been the biggest ever to hit the state, meteorologist Josh Nagelberg said on the AccuWeather.com website.

Many people told tales of narrow misses. "I made it. I got in a closet, put a pillow over my face and held on for dear life because it started sucking me up," said Angela Smith of Tuscaloosa, whose neighbor was killed.

President Barack Obama will visit Alabama Friday to view damage and meet the governor, the White House said.

In preliminary estimates, other state officials reported 32 killed in Mississippi, 30 in Tennessee, 11 in Arkansas, 14 in Georgia, eight in Virginia and two in Louisiana.

The Browns Ferry nuclear power plant in Alabama was expected to be shut for days, possibly weeks, as workers repaired damaged transmission lines.

But the backup systems worked as intended to prevent a partial meltdown like the nuclear disaster in Japan.

"The reactors will remain shut until we have restored the reliability of the transmission system," said Ray Golden, spokesman for the Tennessee Valley Authority, which owns the 3,274-megawatt plant.

Up to 1 million people in Alabama were left without power.

It is too early to estimate the financial cost of the storms, Alabama's state insurance department said.

Federal Emergency Management Agency (FEMA) Administrator Craig Fugate said it is too early for his agency to give a confirmed overall death toll and authorities are concentrating on rescue and recovery.

Some of the worst devastation occurred in Tuscaloosa, where at least 37 people were killed, including some students.

"It sounded like a chain-saw. You could hear the debris hitting things. All I have left is a few clothes and tools that were too heavy for the storm to pick up. It doesn't seem real," said student Steve Niven, 24.

"I can buy new things but you cannot replace the people. I feel sorry for those who lost loved ones," Niven told Reuters.

Shops, shopping malls, drug stores, gas stations and dry cleaners were all flattened in one section of Tuscaloosa, a town of around 95,000 in the west-central part of Alabama.

OBAMA ORDERS AID

Tornadoes are a regular feature of life in the U.S. South and Midwest, but they are rarely so devastating.

Obama declared a state of emergency for Alabama and ordered federal aid.

"Our hearts go out to all those who have been affected by this devastation and (we) stand ready to continue to help the people of Alabama," he said in a Twitter message Thursday.

Governor Bentley also declared a state of emergency in Alabama and said he was deploying 2,000 National Guardsman. Governors in Arkansas, Mississippi and Tennessee also declared states of emergency.

Wednesday was the deadliest day of tornadoes in the United States since 310 people lost their lives on April 3, 1974, weather forecasters said.

"We have never experienced such a major weather event in our history," said the Tennessee Valley Authority, which operates the Browns Ferry nuclear plant and provides electricity to 9 million people in seven states.

"Everybody says it (a tornado) sounds like a train and I started to hear the train," Anthony Foote, a resident of Tuscaloosa whose house was badly damaged, told Reuters. "I ran and jumped into the tub and the house started shaking. Then glass started shattering."

The campus of the University of Alabama, home of the famous Crimson Tide football team, was not badly damaged but some students were killed off campus, Bentley said.

Damage in Alabama was spread over a wide area through the north and central part of the state, said Jennifer Ardis, Bentley's press secretary. (Additional reporting by Peggy Gargis in Birmingham and Leigh Coleman in Biloxi, Colleen Jenkins in St. Petersburg; writing by Matthew Bigg and Pascal Fletcher; Editing by Will Dunham)