Retailers reported the biggest monthly sales gains in two years as Easter and warmer weather sparked demand for spring clothing from American consumers undeterred by higher gasoline prices.

Wal-Mart Stores’s comparable sales rose 6.8%, the largest increase since August 2003. Federated Department Stores, Target, Gap, Talbots, and Limited Brands exceeded analyst sales estimates. The International Council of Shopping Centers said April sales rose 6.6%.

Apparel retailers led the gains as shoppers bought dresses, shorts, and T-shirts after the weather improved. The April increases spurred J.C. Penney Company to boost its first-quarter profit forecast and may help other retailers post higher earnings reports later this month. Increases in gasoline prices, which rose 12% in April, could limit spending in May and June, an analyst at ING Investments, Arun Daniel, said.

“A lot of stores had a particularly good Easter,” said Dan Poole, who helps manage about $34 billion in assets at Cleveland-based National City Corporation, including Kohl’s Corporation shares. “So far the gas price impact is modest. We’ll see if the next move is back to $3 or $4. That will tell a lot.”

Shares of Wal-Mart fell 18 cents to $46.50 at 1:48 p.m. in New York Stock Exchange composite trading. Target dropped 27 cents to $53.12. J.C. Penney rose 36 cents to $66.07.

The ICSC, whose survey was based on data from 59 retailers, had forecast a gain of as much as 6.5%. The Goldman Sachs same-store sales index gained 6.7%. More than 60% of retailers exceeded analyst estimates, according to research firm Retail Metrics. Specialty apparel retailers had the biggest increases, followed by discounters and department stores.

“Retail in general did better than expected,” the chief executive of Federated Department Stores, Terry Lundgren, said in an interview yesterday. “There had been worries and concerns about the economy, yet one report after another shows that the economy is performing well.”

Wal-Mart forecast a May increase of 2% to 4%.Target,the second-largest discount retailer in America, said sales at stores open at least a year rose 10.4% in April, more than its forecast. It estimated a gain of 4% to 6% for this month.

Kohl’s Corporation had a 13.4% increase. Costco Wholesale Corporation, the largest American warehouse-club retailer, lifted sales 7%.

Federated said sales fell less than 1%, a smaller drop that the company and analysts had forecast. May sales may rise 4% to 6%, it said.

J.C. Penney, the third-largest department store chain in America, posted a 2.6% gain. The company raised its first quarter profit forecast 8 cents to 88 cents a share.

Sales at Gap, the largest American apparel chain, declined 3%, less than the 5% drop analysts predicted.