Despite the two-day rally, three major indexes posted an average two-percent fall and the financial sector remained weak.
The Dow Jones industrial average gained 125.71 points, or 1.13 percent, to 11,269.02. The Standard & Poor's 500 was up 6.17 points, or 0.53 percent, to 1,178.81. The Nasdaq Composite Index rose 15.30 points, or 0.61 percent, to 2,507.98.
The US Commerce Department said retail sales strengthened in July by 0.5 percent, led by a spurt in auto sales, which continued to rebound, rising 0.4 percent, following a 0.7 percent jump in June. This added signs of an improving economy.
In Europe, regulators of major European exchanges banned the short selling of financial shares, trying to protect financial companies from speculators and to help restore market confidence. As a result, European bank stocks rallied and pared some this week's losses Friday.
Analysts said that the markets were still fragile and sensitive as uncertainties about US and European economies remained. They predicted equities will still see great volatility next week.