TEHRAN (AFP) - The number of HIV/AIDS infections in Iran is far higher than previously thought because of a large rise in intravenous drug use, a health ministry official was quoted as saying.

"About 40,000 of the total number of intravenous drug addicts are infected with HIV," said Iran's deputy health minister, Moayed Alavian on Tuesday.

"If no action is taken against the spread of this disease as quickly as possible, the number of those infected will reach 100,000 by the end of the next Iranian year (March 2008)," he warned.

Officials have given a variety of lower estimates in the past, most recently saying that the number of HIV/AIDS cases stood at around 20,000.

Iran is believed to have at least two million regular drug users -- and possibly as many as 3.5 million -- and Alavian said addiction is growing by around eight percent a year.

Intravenous drug use is believed to be the main cause of infection at 62.3 percent, followed by unknown causes at 27.9 percent and sexual contact at 7.4 percent.