The French site for the EuroMillions lottery was hacked on Sunday with warnings denouncing gambling as impure and the work of the devil.
The messages appeared in Arabic and French and blocked the homepage of the lottery in France. The hackers identified themselves as "Moroccanghosts."
The French version of the message said: "Oh you believers. Wine, games of chance, statues all augur impurity and are the work of the devil."
It exhorted people to quit gambling, saying it was used by the devil along with alcohol to "sow hatred between yourselves and turn you away from God and prayer".
Gambling and alcohol are forbidden in Islam.
France has a population of 65 million, including an estimated four million Muslims, the largest Islamic population in western Europe.
The EuroMillions lottery, launched in 2004, is now played by nine countries across western Europe: Austria, Belgium, Britain, France, Ireland, Luxembourg, Portugal, Spain and Switzerland.
More than 100 million euros are up for grabs in a EuroMillions jackpot to be played on Tuesday.
Explore further: Fitbit to Schumer: We don't sell personal data