OKLAHOMA CITY, Oklahoma (CNN) -- President Clinton toured tornado-ravaged Oklahoma by helicopter Saturday, getting a first-hand look at the damage wrought by this week's killer storms.

More than 70 twisters killed at least 46 people in Oklahoma and Kansas on Monday. The same line of storms killed another five people in Tennessee and Texas later in the week, and four people are still missing.

After the half-hour flight, Clinton got an even closer look at the damage on the ground in Del City, Oklahoma, one of the state's hardest hit areas.

"I have been going to these sites for 20 years ...this is the most devastating tornado I have ever seen," the president told residents of the city. "I have never seen so much complete destruction of homes over so wide an area."

Clinton urged Oklahomans to build "safe rooms" in their homes to protect them from tornadoes, and said the state of Oklahoma would be able to assist low-income families to build the secured rooms.

Clinton added five more counties to those eligible for federal disaster aid, bringing the total number of counties to 16, according to Oklahoma Gov. Frank Keating.

Earlier, the president used his weekly radio address to announce a $12 million temporary jobs program for residents around Oklahoma City. He also said he would ask Congress for an additional $372 million for a federal disaster relief fund.

The worst of the monster tornadoes that clobbered Oklahoma on Monday was rated an F-5, a funnel cloud half a mile to a mile wide with wind speeds between 261 and 318 mph, the National Weather Service said Friday.

It was the most powerful twister ever in metropolitan Oklahoma City, the Weather Service said, and the most serious outbreak of tornadoes in the area in 50 years. Of 76 twisters that swirled around the Plains that day, 40 occurred around Oklahoma City.

The storms killed a total of 41 people in Oklahoma, another five in the Wichita, Kansas, area and one in Texas the next day. The same severe weather system was blamed for four more deaths in Tennessee on Wednesday.

Intense search and rescue operations in the Oklahoma City area have failed to turn up any new victims for the past 48 hours, the state medical examiner's office said Friday.

Among the missing were Barbara and John Potton, two Britons who were touring North America. They have not been heard from since midafternoon Monday, when they were known to be in the Oklahoma City area.

Also missing is 23-year-old Tram Bui, who tried to take cover below a highway underpass when the tornadoes struck; and motorist Mark Edward Nelson, of Midwest City. Nelson was last seen driving a van in the path of the storm, authorities said.

The state's Emergency Management Office reported 3,719 homes or businesses were destroyed and another 1,632 damaged. Kansas authorities reported structural damage to 8,480 homes or businesses, including 1,109 that were destroyed.

Insurance officials have estimated financial losses at $1 billion or more overall. The Sedgwick County Appraiser's Office estimates damage in the affected area of Kansas at up to $146 million.

Correspondent Martin Savidge contributed to this report.

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