Iranian troops have seized a camel caravan carrying two tonnes of drugs in a clash with smugglers near the border with Afghanistan and Pakistan, according to Iran's official news agency.

The BBC's Jim Muir reports on the drug trade in Iran

Army forces also seized weapons and 13 camels left behind by the smugglers near the provincial capital of Zahedan.

Lying on the so-called "Golden Crescent", Iran is a major route for drugs smuggled from Afghanistan and Pakistan to Europe and oil-rich Gulf Arab states.

The country's authorities pursue a running battle along the border to stem the flow of narcotics, and to curb their own growing drug problems.

Casualties of the drugs war

The battle against narcotics involves a high price.

More than 2,500 security officers have lost their lives in what military officials say amounts to full-scale war along Iran's eastern border.

Iran destroys enough captured narcotics to supply the addicts of three European countries for a year

General Mohammad Fellah, who heads Iran's anti-drug campaign, has lost many colleagues to well-armed traffickers.

"Most of my friends who were chief law enforcement personnel in the eastern part of the country have been martyred crashing in the planes, helicopters, reconnaissance planes," General Fellah says.

And the cost of combating the drugs menace does not stop there.

General Fellah believes that what cannot get past via the borders eventually finds its way through the country, which adds to the domestic drugs problem.

Iran's growing problem

Blocking the flow of drugs to the West appears to mean that some of the narcotics filter back inside Iranian society.

Afghanistan is a major producer of marijuana

Iran officially admits to having two million users of drugs, among them 1.2 million addicts, but some say the true figure may be more than twice that.

Large sums are being spent on propaganda and education campaigns. It is no longer a taboo subject - huge placards are displayed on busy Tehran streets, highlighting the evils of addiction.

Rehabilitation clinics are also available where addicts can seek treatment without fear of prosecution.

Demanding efforts

Iran's efforts to block the smuggling routes from the east have won high praise from international officials.

Between 80% and 85% of all opium and heroin that is seized in the entire world has been seized in Iran alone.

And Europe is benefiting from Iran's sacrifices, but for Iran, this is a costly war on two fronts - one along the border, the other within its own society.

Michael von der Schulenburg, former United Nations co-ordinator in Iran, says: "What we very much regret is that there is still so little international collaboration with Iran, although Iran fights a war also for Europe.