Americans stepped up their online shopping and bought more autos in April, suggesting that consumers may be spending more than indicated by a slump among major retailers. In a reassuring signal, the Commerce Department said Friday that retail sales climbed a seasonally adjusted 1.3 percent last month after a drop in March led by declining car sales. But autos recovered in April, with sales jumping 3.2 percent. Sales growth was uniformly strong, online and off: Online purchases advanced 2.1 percent. Clothiers, restaurants, sporting goods stores, grocers, gas stations and even the embattled department store sector posted higher sales, AP reported. Only building materials stores suffered a monthly decline, though their annual sales growth was solid. Over the past 12 months, total retail sales have risen 3 percent.