Hackers shut down the betting website of bookmaker Paddy Power, demanding a ransom in return for putting the service back on line, it has emerged.

The attack left the site, which attracts thousands of users each day, out of commission for several hours late Wednesday, Paddy Power said yesterday.

But it insisted the hackers demands for payment were not met and that security at the page, which contains customer credit card details, was not breached.

Computer crime police in Britain are attempting to track down the hackers behind the "denial of service" assault on Paddy Power's UK-based webservers. A spokeswoman for Paddy Power said it was confident the criminals would be caught and that the bookmaker would not be forced off-line again.

The timing of the attack was apparently random as it did not coincide with any major sporting event, she said.

"No material loss" was suffered while the site was off-line, the company said in the statement.

"As with any denial of service attacks there was an attempt by the perpetrators to secure payment... No payment was made and the incident is under investigation," the statement continued.

Paddy Power's was the latest gambling site targeted by hackers. Denial of service hacks forced several US bookmakers off-line during Super Bowl weekend. A number of other sites paid "protection money" to keep their services running during Super Bowl, according to the International Data Group (IDG).

Denial of service stings operate by bombarding a site with a huge amount of requests.