By Jill McGivering BBC correspondent in Bangkok

The authorities in Thailand are imposing a night curfew on certain internet games in an effort to curb addiction amongst young people.

The curfew, which starts on Tuesday, is a short-term experimental measure which will be reviewed at the end of September.

Children as young as seven are becoming addicted

Much of their concern is focused on the new role-playing game recently introduced in Thailand called Ragnarok which has proved particularly addictive and led to young players exchanging large amounts of money to improve their performance.

The success of Ragnarok has taken Thailand by storm. Introduced only six months ago, it already has 600,000 registered players here.

It offers a complex virtual world in which players take on the identity of a character and can play indefinitely, competing for power, weapons and status.

Unofficially, there is a cash element too. Points gained during play can be used to buy weapons or improve performance.

But in Thailand, players are buying and selling these points in the real world for money, sometimes large amounts.

Local newspapers say children as young as seven are becoming addicted and even getting into debt. Now the authorities have decided it's all getting out of hand.

Cheap access

They're going to block Ragnarok and games like it from 10pm until six in the morning.

Some people have also called on parents to spend more time with their children and help them to put games like this into a healthier perspective.

Access to the internet is very cheap in Thailand. Many cafes charge only about 30 to 40 US cents an hour.