Costco's December same-store sales beat analysts' expectations, helped in part by online sales in the United States and Canada.
Sales at stores open at least a year rose 3 percent in the five weeks ended Jan. 5, including the impact of fuel sales and foreign exchange.
(Read more: USholiday sales better than last year: MasterCard)
Kevork Djansezian/Staff | Getty Images
On that basis, analysts expected same-store sales to rise 1.8 percent for the month of December, according to a Thomson Reuters poll.
December net sales rose 6 percent to $11.53 billion.
(Read more: Bleak Christmas for top UK supermarkets)
Excluding the negative impact of foreign exchange and falling gasoline prices, same-store sales rose 5 percent.
Costco, which competes with BJ's Wholesale Club Inc and Wal-Mart Stores Inc's Sam's Club, offers everyday items like bananas below supermarket prices, hoping customers will buy other goods as well. It usually prices gasoline lower than competing stations.
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