DUBAI, July 14 (Reuter) Iran hanged 12 convicted drug smugglers in public in the country's northeastern region, a major route of narcotics trafficking from neighbouring Afghanistan, an Iranian newspaper said on Monday. The Kayhan daily said the 12 were executed in the city of Mashhad after they were convicted by an Islamic court of belonging to armed gangs of drug smugglers. It did not say when the sentences were carried out. Tehran said on Sunday police seized 503 kg (1,100 lb) of narcotics and arrested one drugs smuggler in the province. Iran is a key transit route for drugs, mostly opium from which heroin is made, being smuggled to Europe via Turkey from Afghanistan and Pakistan the socalled ``Golden Crescent.'' Tehran has said police seized 175 tonnes of drugs in the Iranian year which ended on March 20. Iranian officials say there are about half a million drug addicts in the country. Media reports have put the number at up to a million. According to Iranian law, possession of five kg (11 lb) of opium or 30 grams (just over one ounce) of heroin is punishable by death. More than 1,000 people have been executed in drugrelated cases since the law took effect in 1989. 12:45 071497