CORPUS CHRISTI, Texas (AFP) - Lashing rain and whipping gusts battered the US-Mexico coast Wednesday as Hurricane Dolly increased to a category two storm and churned toward landfall in southern Texas, forecasters said.

Bracing for as many as 51 centimeters (20 inches) of rain in some areas, authorities worried whether levees could sustain the flood waters after thousands had already fled for safer ground.

Texas Governor Rick Perry issued disaster declarations in 14 counties across the southern portion of the state, and hundreds of National Guard troops and other emergency crews were deployed in advance of the storm.

A category two storm on the five-level Saffir-Simpson scale, the hurricane had higher sustained winds of 160 kilometers (100 miles) per hour and was about 60 kilometers (35 miles) southeast of the Texas border town of Brownsville at 1700 GMT, the National Hurricane Center said.

The force of the storm pounded the coast of the Gulf of Mexico as the hurricane moved to the northwest at 11 kph (seven mph).

"The eye of Hurricane Dolly will be crossing the coast along the southern Texas coast in a couple of hours," NHC said.

Isolated tornadoes could hit South Texas today and tonight, and the rains were "likely to cause widespread flooding across portions of south Texas and northeast Mexico," the NHC said.

The hurricane warning applied to the coast of Texas from Brownsville to Corpus Christi and for the northeastern coast of Mexico from Rio San Fernando northward to the US border.

"It's not going to be a picnic on Padre Island," NHC director Bill Read told CNN, referring to the long, narrow barrier island along the Texas coast that is dotted with resort communities.

The first hurricane of the season in the gulf prompted some oil companies to evacuate personnel from their offshore rigs, but by early Wednesday the storm looked set to bypass the major oil producing areas in the Gulf.

However, concerns were raised about the ability of levees to withstand the floodwaters, which could go as high as three feet (one meter) in southern Texas's Cameron County, officials told the local Brownsville Herald.

"I ask that any residents that live near the levee in Cameron County to please move away from the river levees near the Rio Grande River. We believe those will be breached if the path continues," said Johnny Cavazos, emergency management coordinator for the county.

Authorities called for the evacuation of more than 23,000 people from coastal areas in the Mexican state of Tamaulipas, Governor Eugenio Hernandez said, adding that he had requested the federal government to declare a state of emergency in his jurisdiction.

Accumulation of 20 to 30 centimeters (eight to 12 inches) rain was forecast, with isolated areas expected to see as many as 51 centimeters (20 inches) along with massive waves and flooding at the point of impact, the NHC said.

"Coastal storm surge flooding of six to eight feet (1.8 to 2.4 meters) above normal tide levels along with large and dangerous battering waves can be expected near and to the north of where the center makes landfall," it added.

The NHC has forecast an especially active 2008 weather season, saying there could be up to nine hurricanes and 12 tropical storms in the Atlantic region. The Atlantic hurricane season runs from June 1 through the end of November.

About 35 million people live in the most hurricane-prone US region, the southeastern coastline running from the states of North Carolina to Texas, according to the US Census Bureau.

LIKE IT?  LET OTHERS KNOW