U.S. retail sales at discount, chain and department stores rose in the latest retail week, led by back-to-school and electronics sales, Instinet Research reported in its weekly Redbook Retail Sales Average on Tuesday.

The Redbook Average gained 0.4 percent during the first three retail weeks of August, above last week's 0.2 percent rise and compared with a target 0.2 percent decline, Redbook said.

On a year-over-year basis, sales grew 2.9 percent during the first three weeks of August, above last week's 2.5 percent gain and ahead of the 2.2 percent target.

``Merchandise trends over the past week continued with the back-to-school theme, focused on children's clothing, basic apparel and other school supplies,'' Redbook said.

A number of stores reported an increase in customer traffic, Redbook said.

The Redbook Retail Sales Average is a sales-weighted average of annual growth in same-store sales at discount, department and chain stores that report their results on a weekly basis.

The average is compiled from a sample of general merchandise retailers representing about 9,000 stores. Same store sales measure revenues at stores open at least a year.

The Redbook Average is released weekly by Instinet Research, a division of Instinet, a Reuters-owned electronic brokerage.