Tropical storm Igor has formed in the Atlantic Ocean off the coast of Africa near the Cape Verde Islands and has top sustained winds of nearly 65 km/h.

Forecasters at the U.S. National Hurricane Center in Miami said Wednesday that Igor was moving toward the west at about 13 km/h.

The centre of the storm is expected to pass south of the Cape Verde Islands by Thursday.

A tropical storm watch has been issued for the southern Cape Verde Islands.

Some slow strengthening is expected over the next two days.