The European Central Bank said on Thursday its website had been hacked and some email addresses and other contact information stolen but insisted no market-sensitive data were affected.
The theft came to light after the central bank received an anonymous email on Monday night demanding money in exchange for the addresses.
The hackers broke into a database storing details of people who had registered for ECB conferences, visits and other events, the bank said. That database was kept physically separate from internal systems, it added.
"No internal systems or market sensitive data were compromised," the ECB said in a statement.