Isaac reaches hurricane strength: hurricane center

Isaac reached hurricane strength on Tuesday with maximum wind speeds of 75 miles (120 kilometers) as it bore down on the northern US Gulf Coast, the National Hurricane Center said.

"Reports from an air force reserve hurricane hunter aircraft indicate that maximum winds associated with Isaac have increased to 75 mph (120 km/H)," the center said. "On this basis, Isaac is being upgraded to a hurricane."

The category one hurricane was about 75 miles (115 kilometers) southeast of the mouth of the Mississippi River, and 160 miles (250 kilometers) southeast of New Orleans, the center said .

The storm bore down on New Orleans almost seven years to the day after the city was swamped by Hurricane Katrina, a more powerful storm that devastated the northern coast of the Gulf of Mexico.