In the wake of a massive data breach, Target Corp. may have suffered another blow--reduced customer traffic over one of the busiest shopping weekends of the year.

The number of transactions at Target slipped 3% to 4% compared with the final weekend before Christmas last year, estimates retail consultancy Customer Growth Partners LLC.

By contrast, transactions at other retailers were strong.

A spokeswoman for Target declined to comment specifically on this weekend's results, saying the retailer reports sales on a quarterly basis. Target tried to limit the damage by offering a 10% discount to all customers in its U.S. stores over the weekend, and analysts said that effort helped.

"This is the worst possible time something like this could happen," said Craig Johnson, president of Customer Growth Partners. His firm estimates that U.S. retail sales on Saturday totaled $17 billion, exceeding those on Black Friday by $2 billion.

"Still, American consumers can be forgiving if you're honest with them--and the discounts help."

Financial institutions, meanwhile, began to take steps to contain their potential losses stemming from the data-security breach at Target, in which the credit-card and debit-card accounts from more than 40 million customers were compromised by hackers who infiltrated the card-swipe machines at the checkout counter. The breach began Nov. 27 and wasn't halted until Dec. 15.

J.P. Morgan Chase & Co. slapped daily spending limits on debit-cards that had been used at Target stores during the period in question. Citigroup Inc., meanwhile, in some cases may lower limits, block transactions and reissue cards for debit-card holders if it sees suspicious activity, a person familiar with the matter said Sunday.

On Sunday, J.P. Morgan opened a third of its U.S. branches--especially those in areas near major shopping centers--to help its debit-card holders access more cash after it temporarily limited daily cash withdrawals to $100 and capped total daily spending at $300. Chase is planning to replace the debit cards within two weeks. The spending restrictions don't apply to credit-card users, the bank said.

"We realize this could not have happened at a more inconvenient time with the holiday season upon us," according to a Chase statement on its website. "We are taking these precautions to combat fraud."

Other major card issuers said they haven't reined in transactions. American Express Co., Wells Fargo & Co. and Capital One Financial Corp. haven't made any changes to transaction limits.

Target said on Friday there had been very few occurrences of fraud so far, but the investigation is still in its early days and the extent of the damage won't be known for some time.

While it is common for banks to reissue cards when large numbers of customers are potentially affected by a breach, some financial institutions may wait to take such steps because of the frequency of breaches and the cost of reissuing cards.

"It's just impractical for most banks to replace cards on a regular basis," said Al Pascual, senior analyst of security, risk and fraud for Javelin Strategy & Research, a Pleasanton, Calif., payments-research firm.

Customers are concerned. In New York City, Jarellis Jimenez, 32 years old, who shopped at Target twice during the period of the security breach, said she made an appointment Monday with her bank to review her financials. Despite the breach, she continues to shop at her local Target, purchasing some toys for Christmas Sunday. "I like the products they sell here," Ms. Jimenez said.

Just a block up the road, a local Chase bank was open with candy canes on offer inside and a sign saying "here to help."

Dan Fitzpatrick contributed to this article.

Write to Shelly Banjo at shelly.banjo@wsj.com, Sara Germano at sara.germano@wsj.com and Andrew R. Johnson at andrewr.johnson@wsj.com