Hurricane Isaac surged ashore in southern Louisiana on Tuesday, packing high winds and heavy rains, and was set to hit New Orleans seven years to the day after Hurricane Katrina devastated the city.

Isaac is the first hurricane to make landfall in the US this season. While not packing nearly the power of Katrina -- which was a Category 3 storm when it slammed the Crescent City on Aug 29, 2005 -- Category 1 Isaac was nevertheless a powerful reminder of New Orleans' vulnerability.

The hurricane will be the first test for multibillion-dollar flood defenses built after levees failed under Katrina's storm surge and left large parts of New Orleans under water.

The National Hurricane Center warned late on Tuesday that Isaac and its 80 mph (130kph) winds were producing a dangerous storm surge and that flooding from rainfall would follow.

Isaac will also test the resolve of officials and preparedness of a city where some 1,800 died seven years ago in what was the costliest natural disaster in US history.

Earlier on Tuesday, officials from Mitch Landrieu, the mayor of New Orleans, to Louisiana Governor Bobby Jindal, to US President Barack Obama, scrambled to get ahead of the storm's impact, mindful of the chaos and botched relief efforts in the wake of Katrina.

Landrieu assured residents that this time around, 'your city is secure,' and said emergency services were ready for search and rescue missions, if needed.

'We're in the heart of this fight,' Landrieu told an evening news conference. 'We are in the hunker-down phase.'

About 1,000 US National Guard troops in military vehicles took up positions in the mostly deserted streets of New Orleans, brandishing automatic assault rifles to ward off any threat of the looting that spread after Katrina. Police cars patrolled darkened streets with blue lights flashing.

Obama urged residents to take cover and heed warnings, saying that now was 'not the time to tempt fate.' . He issued emergency declarations for Louisiana and Mississippi earlier this week.

Isaac's arrival on the seventh anniversary of Katrina cast a spotlight on the enduring struggle of the iconic American city and its residents.

When the 2005 storm hit, the city endured days of chaos, including widespread looting and other crimes. Hundreds drowned while residents waited for days to be plucked from their rooftops by Coast Guard helicopters.

Hundreds of thousands of residents, their homes destroyed by flooding or made uninhabitable by mold, were moved temporarily to Texas and other states. Thousands along the Gulf Coast lived in government provided trailers for months or years afterwards.

After Katrina, the Army Corps of Engineers built a $14.5 billion defense system of walls, floodgates, levees and pumps designed to protect the city from a massive tidal surge like that caused by Katrina.

On Tuesday morning, army engineers closed the massive new floodgate at Lake Borgne, east of New Orleans, for the first time. It is largest storm-surge barrier in the world.

Officials have confidently predicted that the systems will stand up to the test, although residents have been wary.

Most of the city's Lower Ninth ward, scarred by memories of Katrina, was deserted on Tuesday. Residents who did not evacuate stocked up on water, food and fuel.

'We've got all kinds of eats and treats,' Arthur Anderson, 61, who was trapped in the attic of his house during Katrina before he escaped by boat.

Residents of Louisiana's low-lying Plaquemines Parish, where some flooding was already happening on Tuesday, were anxious about their homes.

At 10 pm CDT (0300 GMT), the Hurricane Center said Isaac was centered about 75 miles (120 km) southeast of New Orleans with top sustained winds of 80 miles per hour (130 kph).

The storm was traveling at a relatively slow 8 mph (13 kph), which was a worry as slow-moving cyclones can bring higher rainfall. Landrieu said the city's pumping capacity could cope with about one inch of rain per hour. - Reuters