(From top) A police car abandoned on Canal Street, New Orleans, a man waits for the Superdome, which was converted into an emergency shelter, to open and a woman walks in the deserted French Quarter. (Reuters, AFP)

New Orleans, Aug. 29 (Reuters): Hurricane Katrina tore into Louisiana today, although the massive storm appeared to spare low-lying New Orleans a feared death blow and delivered much of its force to neighbouring Mississippi and Alabama.

Historic New Orleans, which has long feared extinction if a massive hurricane made a direct hit, endured extensive damage from Katrina's 216 kmph winds after the storm came ashore from the Gulf of Mexico and roared along the coast.

By 1700 GMT Katrina’s winds had decreased to 170 kmph, a Category 2 storm, with higher gusts and its centre was moving ashore at the Louisiana-Mississippi border.

The bowl-shaped city’s levee system appeared to be holding off the Mississippi river and Lake Pontchartrain on its edges. Officials said a breach occurred in nearby St Bernard Parish, where Katrina’s eye passed and extensive damage was expected.

“Please Pray for New Orleans” read a giant hand-painted sign, appearing to sum up the fears that had seized the city known as The Big Easy for its relaxed life and party atmosphere.

About 150 people were reported stranded on rooftops in that southeastern Louisiana parish, where officials said 2.5 to 3 meters of water swamped the region.

“We’re getting reports that (more than 20) buildings are collapsing throughout the city,” New Orleans mayor Ray Nagin said, adding it remained unsafe at midday. “This city is under siege by Katrina.”

However, Katrina’s slight eastern turn that might have saved New Orleans brought its powerful winds and tides into Mississippi coastal tourist havens of Biloxi and Gulfport.

The National Hurricane Center said the exposed Mississippi coastline could expect 4.5- to 6-metre storm surges. Mobile Bay in Alabama was swelling on Katrina’s approach.

Winds sent debris flying through the New Orleans’ streets, blew windows out of high-rise hotels and tore through the roof of the Superdome, where US Senator Mary Landrieu said 10,000 people had taken refuge.

Governor Kathleen Blanco said in a news conference the damage had caused leaks and evacuees had been moved to dry areas in the stadium, but there was no immediate danger. Weather experts had predicted thousands of homes could be damaged or destroyed and a million people left homeless if the storm surge is too great for the levees to hold back.

Officials estimated a million people had left the area ahead of the storm, which was once a fearsome Category 5 with winds of 282 kmph, but many chose to ride it out. It hit land as a Category 4 on the five-step Saffir-Simpson scale.

President George W. Bush today approved “major disaster declarations” for the states of Louisiana and Mississippi, White House spokesman Scott McClellan said.