WASHINGTON - Hurricane Ike strengthened rapidly into an "extremely dangerous" Category 4 storm in the Atlantic Ocean with 135 mph (215 kph) winds late on Wednesday, the U.S. National Hurricane Center said.

Ike was moving west-northwest but was expected to take a turn to the west on Thursday night and Friday, taking it over the open waters of the west-central Atlantic.

It was still too early to tell what if any land areas might be affected by Ike, or whether it would threaten the oilfields in the Gulf of Mexico, the Miami-based center said.

The hurricane center's Web site, with updates and graphics.

(Reporting by Todd Eastham; editing by John O'Callaghan)