At least one million people along the Texas coast were deserting their homes as hurricane Ike, expected to intensify into a fearsome category 4 storm, churned menacingly towards them, threatening the US' biggest refinery clusters as well as NASA facilities.

Met officials say the storm, that ravaged homes in Cuba and killed at least 81 people in the Caribbean, could slam into the Texas coast -- south of Galveston -- as a powerful category 3 storm late Friday or early Saturday and may intensify into category 4.

Mandatory and voluntary evacuations were planned or underway in at least seven coastal counties.

Ike is expected to be the state's biggest challenge since 2005's Hurricane Rita triggered a massive evacuation of Houston.

Aransas County has ordered a mandatory evacuation of all non-essential government employees.

In Galveston, city officials ordered mandatory evacuations for part of the island town. The rest of the town will be under a voluntary evacuation order.

The storm continues to move across the Gulf of Mexico and is expected to strengthen, but it is still too early to know how strong it will become or exactly where it will come ashore, Houston Chronicle reported.

Texas capital Houston could face some of the storm's strongest winds, the report said.

Texas Senator John Cornyn, estimated that as many as one million people could head for higher ground before Ike comes ashore.

Texas is home to 26 refineries that account for one-fourth of America's refining capacity. NASA's Johnson Space Centre also lies in areas that could be vulnerable to wind and damaging floodwaters if Ike crashes ashore as a major hurricane, US media reports said.