Parts of Oklahoma City were being evacuated as fire reached the northeastern edge of the city of half a million people, according to local broadcaster KOCO-5.

Parched Oklahoma's emergency preparedness agency said fires have burned in two dozen counties in the last five days and the state was bracing for "extremely dangerous" wildfire conditions.

Oklahoma Governor Brad Henry said he has asked President George W. Bush to declare an emergency in the state and commit federal resources to battling the fires, which have scorched huge swaths of the largely rural state since Tuesday.

"Most of these fires are caused by human carelessnes. We are asking people to use extreme caution," Henry told CNN television. "We are literally at the mercy of the weather. We have no appreciable precipitation forecast."

Residents of a largely rural district northeast of downtown Oklahoma City were forced to flee their homes late Sunday as strong westerly winds fueled the latest fire, the network said.

Henry told reporters that conditions on the ground amounted to a "perfect storm" for fires and pledged "every form of assistance available" for the hundreds of firefighters battling the blazes. Many of the firefighters are volunteers.

"I want to stress that even though our firefighters and first responders have done a fabulous job fighting these fires, that the danger is not over," Henry said.

Three deaths in Texas and one in Oklahoma have been blamed on the fires, authorities said. Firefighters from North Carolina, Alabama, Tennessee and Florida have been brought in to fight the fires but gusty winds have played havoc with the work of fire-battling helicopters and tanker planes.

High temperatures and wind powered the fires, which left a 68-year-old woman dead from burns and smoke inhalation, according to the emergency preparedness agency.

About 200 homes and businesses and 250,000 acres of land have been hit by wildfires in Oklahoma since November, it said.

The wildfires were threatening about 200 homes in northern Texas, where at least three people have in fire-related incidents, according to CNN.

"We're trying to get people to evacuate and leave before the fires get there because, with this heat and low humidity, it's taxing our resources," a Texas government spokesman, Sparky Dean, told the network.

Central Oklahoma has had only a quarter-inch (.63 cm) of precipitation since the end of October. High temperatures in recent days have ranged around 80 degrees Fahrenheit (27 degrees Celsius), and strong, gusty winds have hampered firefighters' efforts, state Fire Marshal Robert Doke said.

"We are extremely busy -- more so than we expected for this time of the year," Doke told CNN. "The bulldozers do great, but by the time we get them dispatched to one area and get them working, we've got other fires," he said.

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