VIENNA, Austria - Marijuana vending machines in Los Angeles violate international treaties and should be shut down, the U.N.-affiliated drug control board said Friday.

"The International Narcotics Control Board is deeply concerned about reports that computerized vending machines to dispense cannabis (marijuana) have been put into operation in Los Angeles," Philip O. Emafo, president of the board, said in a statement.

At least three Los Angeles medical marijuana dispensaries have installed vending machines to distribute the drug to people who carry cards authorizing marijuana use. The drug is said to alleviate chronic pain, loss of appetite and other ailments.

Supporters say the machines, which dispense 1/8th or 2/8th of an ounce of marijuana at a time, offers users lower drug prices and increases security.

Marijuana use is illegal under U.S. law, which does not recognize the medical marijuana laws in California and 11 other states.

The Drug Enforcement Agency and other U.S. agencies have been shutting down major medical marijuana dispensaries throughout California in the last two years and charging their operators with felony distribution charges.

"We know that the use of cannabis is illegal under federal law of the United States and we trust the authorities will stop such activities, which contravene the international drug control treaties," Emafo said.

In its statement, the Vienna-based drug board also said scientific research about the therapeutic usefulness of cannabis or cannabis extracts was still in progress and had not produced much evidence.