The popular computer game World of Warcraft is "more addictive than crack cocaine", warn experts.

In a report by addiction therapists at Sweden's Youth Care Foundation the game has been described as "the most dangerous game on the market" after a 15-year-old collapsed and went into convulsions after playing it for 24 hours earlier this month, reports The Sun.

The report's author Sven Rollenhagen said: "World of Warcraft is the crack cocaine of the computer gaming world. Some people can't drag themselves away and will play it till they drop."

The game's US makers Blizzard Entertainment have said 11 million people worldwide play World of Warcraft.

Psychiatrist Dr Richard Graham, of London's Tavistock Centre, said: "Some of my clients discuss playing games for 14, 16 hours a day - without breaks and without attending to their physical needs.

"For those, the consequences are potentially severe."