Iranian news agencies say 16 rebels have been hanged in retaliation for the deaths of at least 14 border guards in an ambush on the border with Pakistan.
The ambush happened on Friday night in the south-eastern province of Sistan-Baluchestan.
The hangings took place in a prison in Zahedan, north-east of Saravan but it is not clear what link those hanged had to the attack, the BBC reports.
One report suggests they may already have been tried and convicted, but their executions brought forward following the ambush.
Iran is a major transit route for drugs that originate in Afghanistan and is trafficked across its territory, with much of it bound for Western countries.
AFP quotes officials as saying that more than 4000 police officers and soldiers have been killed in three decades of fighting with drug traffickers.
People smugglers also use the route to traffick illegal immigrants to Europe, via Iran and Turkey.
The Islamic republic says it is fighting a deadly war against drug traffickers who make up half its prison population.
Sistan-Baluchestan province has a history of unrest, with the mainly Sunni Muslim population complaining of discrimination at the hands of Iran's Shi'ite Muslim authorities.
An armed Sunni group, Jundallah, has carried out a number of attacks against the state in recent years.