rices for auto and home insurance have been rising sharply around the country in the last few months as insurers struggle to keep pace with increasing costs, insurance executives and analysts said yesterday.

The two biggest auto and home insurers, State Farm and Allstate (news/quote), have taken the lead in the price increases, and many smaller companies are following, analysts said.

"Both auto and homeowners insurance have lost tremendous amounts of money over the last few years," said Robert P. Hartwig, the chief economist at the Insurance Information Institute, a trade group.

Ronald D. McNeil, a senior vice president for Allstate, told investors at a Banc of America securities conference in New York yesterday that Allstate had increased its prices for auto insurance an average of 8.3 percent in 17 states so far this year. He said Allstate had raised its prices for home insurance by an average of more than 20 percent in 20 states.

State Farm said it was taking similar action. It was not immediately able to provide figures for the increases so far this year. But Richard Luedke, a spokesman, said the increases were significantly larger than those in the previous year, when they averaged 4.6 percent for home insurance and 2.7 percent for auto insurance. The increases were necessary, he said, because "we were paying out more in claims than we were collecting in premiums."

J. Robert Hunter, the director of insurance for the Consumer Federation of America, said that profit and loss trends for the insurers indicated a need for an average increase of 4 percent to 8 percent in auto premiums. But he said increases of 20 percent for home insurance were "way out of line."

"I don't see anything in the data that would justify an increase of that magnitude," he said.

In some states, the increases are even higher, analysts said. "We're starting to see increases of 25 percent to 30 percent in a lot of states," said Ira L. Zuckerman at Nutmeg Securities in Fairfield, Conn.

For years, he said, home insurance was sold as a loss-leader to attract customers to the more lucrative business of auto insurance. But in recent years, both lines of coverage have been losing money.

Auto insurance is the largest line of coverage in the industry, accounting for about $125 billion a year in sales. By contrast, sales for home insurance last year came to $34 billion. Cars far outnumber homes, Mr. Hartwig said, and insurance claims on cars are more frequent and often more expensive. Some claims for injuries, for example, can run into the millions of dollars.

Insurance executives discounted the Sept. 11 attacks as a factor in the rising rates for cars and homes.

Mr. Hartwig said costs for insuring homes had been increasing because of rising expenses for building materials and, for the last two years, a number of relatively small but costly storms. The insurers have also been hit, he said, by costly claims in Texas and California and other states from water damage that has led to the growth of toxic mold.

In some cases, toxic mold has been so extensive that homes have been destroyed and insurers have been forced to pay the full amount of the coverage. In response, insurers are cutting back their coverage for mold and water damage.

Insuring autos has become more expensive, Mr. Hartwig said, because of rising costs for medical services and sharp increases in fraudulent injury claims. In New York, Texas, Colorado and California, the police say gangs stage auto accidents so they can collect money for supposed injuries.

The auto insurers made things worse for themselves by competing fiercely on price, said Michael A. Lewis, an analyst at UBS Warburg. "Now they are stressing rates over volume," he said.

Several insurers began raising prices for home and auto insurance last year, but until recently State Farm had resisted doing so.

The action of the big companies, Mr. Zuckerman said, makes it easier for smaller companies to raise their prices. "If the big guys are raising their prices," he said, "it means the little guys don't have to worry about losing business to the big guys."