Chase says the customers whose debit cards are at risk from a security breach at Target will face $100-limits on cash withdrawals. CNBC's Sharon Epperson reports.

Following the massive credit and debit card security breach at Target stores, Chase bank on Sunday said more than a third of its branches would be open across the country to help affected customers.

"We'll have the highest density in the Northeast, California and Southeast and prioritize branches near major shopping centers or those that have instant issue (where they can reissue debit card on the spot)," the bank said in a statement.

"(Our) employees have been unbelievable offering to work today, the Sunday before Christmas, to help customers," the statement said.

The move comes after JPMorgan Chase, the largest bank in the United States, told customers Saturday that they would be limited to $100 in cash withdrawals and $300 in total purchases per day if they used Chase debit cards at Target during the recent security breach.

The limit applies to about 2 million customer accounts, Kristin Lemkau, a Chase spokeswoman, told NBC News. That represents less than 10 percent of Chase customers, she said. The limit does not apply to Chase credit cards.

Separately, a source familiar with the situation told CNBC that Citibank was also imposing limits on debit cards for affected customers if it sees suspicious activity, though the extent of those limits was not immediately clear.

Target announced earlier this week that as many as 40 million debit and credit cards were compromised during the breach, which the store said began just before Thanksgiving and ended Dec. 15.

The security breach exposed customer names, card numbers, expiration dates and the short security codes known as CVVs. The industry blog Krebs on Security, which first reported the breach, has reported that card accounts are already being sold on the black market.

Target, eager to repair the public-relations damage and restore customer trust, has apologized and offered a 10 percent discount at its stores this week.

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