MIAMI (AP) -- Forecasters say Hurricane Gonzalo has strengthened to a Category 4 storm as it churns in the Atlantic.

The U.S. National Hurricane Center in Miami says Gonzalo has top sustained winds of 130 mph (215 kph) and is about 640 miles (1,025 kilometers) south-southwest of Bermuda. It was moving northwest at 12 mph (19 kph) Wednesday.

Hurricane Gonzalo, lower right, Wednesday as it heads toward Bermuda. (AP Photo/NOAA)

Bermuda's government has posted a hurricane watch for the British territory, urging islanders to keep an eye on the approaching storm. Officials say flights departing Bermuda on Thursday, Friday and Saturday were fully booked.

Authorities on some smaller islands buffeted by Gonzalo say at least one person is dead and two are missing after the storm swept through the eastern Caribbean earlier this week.