WASHINGTON (AP) --€” Americans stepped up their spending at retail businesses in September, reflecting stronger sales of autos, electronics, and building supplies.

Retail sales rose 1.1 percent last month, the Commerce Department said Monday. That followed a 1.2 percent increase in August, which was revised slightly higher. Both were the largest gains since October 2010.

Sales rose in most major categories. Electronics and appliances surged 4.5 percent, in part because of the release of the new iPhone. Sales at auto dealers increased 1.3 percent. Building materials and garden supplies, furniture, and clothing sales all increased, too.

Economists said the September increase should help drive slightly stronger growth in the July September quarter. But they cautioned that some of the jump was driven by the release of the iPhone 5.

"This shouldn't be considered the start of a consumer revival," cautioned Paul Dales, senior U.S. economist at Capital Economics. "This is a one-time boost that will be reversed in the coming months."

Some of the increases were also driven by higher prices. Gas station sales also rose 2.5 percent. And food sales increased 1.2 percent. The recent drought may have driven some food prices higher, economists noted.

Still, excluding autos and gas, sales were still up a solid 0.9 percent in September.

The retail sales report is closely watched because it is the government's first look at consumer spending each month. Consumer spending drives nearly 70 percent of economic activity.

High unemployment and weak pay increases have kept consumers from spending more freely. That has held back growth. The economy grew at a weak 1.3 percent rate in the April-June quarter. Most economists believe growth will stay around 2 percent for the rest of the year.

Despite the weak growth, consumers grew more confident in September. The Conference Board reported its confidence index rose last month to the highest reading since February.

The job market also looked a little better in September. The unemployment rate dropped to 7.8 percent from 8.1 percent in August. It was the first time the rate has been below 8 percent since January 2009.

And U.S. auto companies reported that sales rose 13 percent in September from a year earlier to nearly 1.2 million. Analysts think sales could hit 14.3 million this year, up from 12.8 million last year. The Federal Reserves' aggressive policies have kept interest rates low, encouraging some Americans to replace aging vehicles.

Sales at building materials and garden supply dealers rose 1.1 percent in September. Sales at furniture stores were up 0.4 percent. Sales at specialty clothing stores rose 0.6 percent. Sales at general merchandise stores, a category that includes big retailers such as Wal-Mart (NYSE:WMT) and Target (NYSE:TGT), were up 0.3 percent in September following a 0.3 percent drop in August.

Sales at non-store retailers, the category that covers online shopping, rose 1.8 percent.

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