Sales at U.S. retailers surged in July to the highest level of 2017, aided by strong demand for new autos and Amazon's Prime Day shopping specials.

Sales at retailers nationwide jumped 0.6% last month, the government said Tuesday. Economists polled by MarketWatch had forecast a 0.4% increase.

A mysterious decline in spending at the end of the second quarter, meanwhile, vanished after fresh government revisions based on newly incorporated sales data.

Retail sales actually rose 0.3% in June instead of falling 0.2% and sales in May were flat. The retail report can be quite volatile and subject to large revisions.

The latest report on retail sales shows households still had plenty of buying power as the third quarter got under way in July. Consumer spending is by far the largest source of U.S. economic activity.

Steady hiring, the lowest unemployment rate in 16 years and gently rising incomes have all buoyed spending in 2017, keeping the economy on a modest growth path more than eight years after an expansion took hold.