NEW YORK (Reuters) - Hurricane Ike, which blasted the densely populated Texas coast and swept through Houston on Saturday, could trigger insurance claims between $8 billion and $18 billion, according to early estimates of the damage.

Tom Larsen, a senior vice-president with EQECAT Inc, which helps insurers model catastrophe risk, told Reuters that from data he had seen so far, the cost of damage was likely to fall in the middle of that range.

Another risk modelling firm, AIR Worldwide, said the expected loss to insurers from onshore damage was around $10 billion.

Ike, a massive hurricane that idled more than a fifth of US oil production, came ashore at the barrier island city of Galveston as a strong Category 2 storm in the early hours of the morning with heavy rains and sustained 110 mph (175 kph) winds, the National Hurricane Center said.

But initial reports were that damage was not as extensive as initially feared, with the Galveston and Houston ship channels spared the worst.

Based on the estimates, Ike will not be anywhere near as costly for insurers as Hurricane Katrina three years ago, but at the high end of the estimate could rank as the country's fourth most expensive disaster.

The size of the storm could mean widespread damage.

Peter Dailey, AIR Worldwide's director of atmospheric science, said wind damage was expected to extend "not only along the coast, but ... well over 200 miles inland from Galveston." BLOW-OUT Insurers face a welter of claims from businesses and homeowners in the low-lying areas around Houston, the country's fourth-largest city.

EQECAT's Larsen said windows in Houston high-rises blown out by Ike's strong winds were alone expected to result in costly claims.

"That is expensive, it is a significant cost once salt water gets into the buildings," he said.

Most standard homeowners policies exclude flood damage, and many homeowners across the country do not opt for separate coverage. However, commercial properties do generally carry it.

Larsen said it was likely there would be extensive roof damage for homeowners, and water damage, as a result.

Galveston County, a centre of oil refining and shipping 50 miles (80 km) southeast of Houston, was all but destroyed by a hurricane in 1900.

Katrina is the most costly US catastrophe on record, causing damage that cost more than $80 billion, about half of which was covered by insurers, according to the New York-based Insurance Information Institute, a trade group funded by insurers.

The biggest property insurers in Texas, and the most exposed to claims in the heavily populated coastal region, are State Farm Group, Allstate Corp and Farmers Insurance Group. The three together account for about half of the insurance market in Texas, according to insurance ratings agency A.M. Best.

Other players with smaller market shares include: American International Group Inc , Ace Ltd , Travelers Companies Inc and Chubb Corp.

After Katrina, which cost insurers $41.1 billion, 1992's Hurricane Andrew and the 2001 attacks on the World Trade Center in New York and the Pentagon rank as the No. 2 and No. 3 most-costly US catastrophes, according to the Insurance Information Institute. Insured losses from Hurricane Ike would have to top $17 billion to rank fourth.