Washington - Hurricane Bill gained strength over the Atlantic Ocean on Wednesday, with winds reaching speeds of 215 kilometres per hour as US forecasters predicted its effect would soon be felt in Bermuda.

The US National Hurricane Centre in Miami said Bill, the first hurricane of the season, had become a category 4 hurricane, only one step below the highest strength on the Saffir-Simpson Scale.

The storm was located about 610 kilometres northeast of the Leeward Islands in the Caribbean. It was expected to produce high swells around Bermuda and northern Caribbean nations, the hurricane centre said.

The storm was moving west at 30 kilometres-per-hour, the centre said. A gradual turn north-west was expected later on Wednesday, and the storm was to pass the Leeward Islands on the north.(dpa)