The governor of the southern US state of Georgia on Thursday ordered the mandatory evacuation of the city of Savannah and other coastal areas ahead of Hurricane Irma.

"I encourage all Georgians in our coastal areas that could be impacted by this storm to evacuate the area as soon as possible," Governor Nathan Deal said.

Deal said a mandatory evacuation would take effect beginning on Saturday for Chatham County, which includes Savannah. Chatham County has a population of nearly 300,000 people.