Hurricane Ike ploughed into the densely populated Texas coast near Houston early today, bringing with it a wall of water and ferocious winds and rain that flooded large areas along the Gulf of Mexico.
Ike came ashore at the barrier island city of Galveston as a strong Category Two storm with 175 km/h winds, the National Hurricane Centre said.
The storm was downgraded this morning to a Category One on the hurricane intensity scale, carrying top sustained winds near 145 km/h. It has since weakened to become a tropical storm.
Ike had blown through the Gulf of Mexico for days and covered a vast area extending hundreds of kilometres when it reached the Texas coast. It is the biggest storm to hit a US city since Hurricane Katrina devastated New Orleans in 2005.
The hurricane drove a wall of water over Galveston and submerged a five-metre sea wall built to protect the city after a 1900 hurricane killed at least 8,000 people. More than half of its 60,000 residents had fled and emergency operations were suspended through the storm.
About 80 kilometres inland, Ike lashed downtown Houston's glass-covered skyscrapers, blowing out windows and sending debris flying through water-clogged city streets. Houston is the fourth-largest city in the US.
US president George W. Bush declared a federal disaster area for Texas and ordered aid to supplement state and local recovery efforts in the area struck by Hurricane Ike, the White House said.
Officials said it was too soon to assess the damage and were waiting for a break in the weather to deploy a search and rescue operation.
"We expected a major storm and our expectations unfortunately came true," said a spokesman for Texas Governor Rick Perry. "The weather needs to clear up a little bit to see just what the devastation was."
Around 4.5 million people in the Houston-Galveston area were without power.
Mr Bush warned that the danger had not yet passed as he sought to assure residents his administration would not repeat mistakes made in the handling of Katrina in 2005.
"This is a huge storm that is causing a lot of damage," said Mr Bush. "The storm has yet to pass."
He also pledged to prevent extraordinary gas price increases because of the hurricane, which has shut down 17 oil refineries on the Gulf of Mexico, the heart of the US oil sector where 22 per cent of fuel supplies are processed. Energy experts said it would take at least a week for the refineries to get back to normal.