Some retailers reported stronger-than-expected November sales on Thursday, helped by a post-Thanksgiving rush and holiday discounts, but notable misses by others and a shift in the retail calendar left an unclear picture of the strength of the key holiday season.

Results from discounters Target Corp and Family Dollar Stores Inc fell short of analysts' expectations, as consumers tightened their wallets in the face of rising food and fuel costs, increasing mortgage rates and tighter credit.

Patricia Walker, a senior executive with Accenture's retail practice, said the results were a mixed bag. Retailers that took advantage of all the publicity around Black Friday, the day after the U.S. Thanksgiving holiday that traditionally kicks off the holiday shopping season, were able to boost sales, she added.

The key question for all of these retailers is, can they keep the momentum going in December? Walker said.

A shift in the monthly retail reporting calendar boosted some November same-store sales figures, but will deflate some results in December, helping to disguise the month's true winners and losers.

Target, whose shares fell nearly 7 percent in morning trading, said sales at stores open at least a year, adjusted for the calendar shift, rose 1.1 percent in November, below its planned range of up 2 percent to 4 percent.

If the recent soft trends continue, Target said, its December sales could also miss its forecast.

Target's warning is cause for concern when coupled with comments from other retailers that sales last week were sluggish even after the Black Friday hype, said Ken Perkins, president of research firm Retail Metrics.

Discount rival Wal-Mart Stores Inc said U.S. same-store sales rose 1.5 percent in November, and results were solid as the holiday rush got under way.

The world's largest retailer made an early push to try to drive holiday sales, cutting prices on more than 15,000 items.

Wal-Mart's same-store sales increase was slightly better than analysts had expected and within its planned range. But sales at its namesake stores continue to lag, and it forecast a U.S. same-store sales gain of 1 percent to 3 percent for the holiday-heavy month of December.

Investors will try to sort through the numbers and the impact of the calendar shift to glean insight into the strength of consumer spending, which makes up two-thirds of the U.S. economy.

Rising gasoline prices helped sales at warehouse clubs Costco Wholesale Corp and BJ's Wholesale Club Inc, which operate gas stations. Costco also said more shoppers had come into its stores, and it cited strength in foreign currency, especially in Canada and the United Kingdom.

Department stores, many of which benefited from the calendar shift, offered an unclear picture. Sales at Kohl's Corp Macy's Inc, Nordstrom Inc and Saks Inc topped expectations, while those at J.C. Penney Co Inc Dillard's Inc and Bon-Ton Stores Inc missed.