WASHINGTON — Retail sales in the United States rose 1.3% in April, the Commerce Department announced. It was the largest monthly gain since March 2015 and better than the 0.8% increase economists were ­forecasting.

Core retail sales, which exclude automobiles, gasoline, building materials and food services, shot up 0.9% last month after an upwardly revised 0.2% gain in March. The core retail sales correspond most closely with the consumer spending component of the nation’s economy. Consumer spending accounts for about two-thirds of the nation’s gross domestic product.

Sales in April likely benefited from an extra weekend: there were five last month compared to four in April of 2015.

Every segment of the retail industry saw improved results last month except home centers, whose sales were suppressed by the mild weather.

April’s sales surge was led by three categories: autos, gasoline stations and nonstore retailers, a segment that includes online shopping at sites such as Amazon.com Inc. Department store sales increased 0.3%.

The Thomson Reuters same-store sales index for April registered a 1.4% gain, in contrast to the 2.3% decline a year earlier.

Costco Wholesale Corp. said net sales in the four weeks that ended May 1 increased 3% to about $9 billion. The Issaquah, Wash.-based company said comparable-store sales at U.S. stores rose 2%, excluding negative impacts from pump price deflation and foreign exchange. Costco’s Canadian operation in April posted a 7% rise in same-store sales. The U.S. regions with the strongest results were the Midwest, Texas and the Pacific Northwest, noted Jeff Elliott, Costco’s assistant vice president of finance and investor relations. The weakest U.S. comps were from California.

Discount store operator Fred’s Inc. said sales for the four weeks to April 30 increased 1% to $162.2 million. Fred’s said comparable-store sales rose 0.3%, compared to a 0.7% increase in the year-earlier period.