Israel said on Saturday that the online publication of thousands of its citizens' credit card details by a hacker claiming to be Saudi was comparable to terrorism, and it vowed to hit back.

The data theft, which appeared to focus on commercial Web sites, was one of the worst Israel has said it has faced. While the financial damage was reportedly minimal, the breaches have heightened concerns about the potential use of stolen information by the Jewish state's foes.

Such cyber-attacks are "a breach of sovereignty comparable to a terrorist operation, and must be treated as such," Deputy Foreign Minister Danny Ayalon said during a speech at a community center.

"Israel has active capabilities for striking at those who are trying to harm it, and no agency or hacker will be immune from retaliatory action," he said, without elaborating.

The hacker, identifying himself as Saudi-based OxOmar, said on Thursday that he had leaked private information about more than 400,000 Israelis. Credit card company officials said around 25,000 numbers, some of them expired, had been posted as of Friday.

After Israeli media ran what they said were interviews conducted with OxOmar over e-mail, the Haaretz newspaper said a blogger had tracked the hacker down and determined he was a 19-year-old citizen of the United Arab Emirates studying and working in Mexico.

An aide to Ayalon, Lital Shochat, said Israel was aware of the report but had not yet requested help from Mexican authorities.

(Writing by Dan Williams; Editing by Alessandra Rizzo)