GENEVA - Iran executed nearly 1,000 prisoners last year, the highest number in two decades, and hundreds of journalists, activists and opposition figures languish in custody, a United Nations investigator said on Thursday.Ahmed Shaheed, UN special rapporteur on human rights in Iran, voiced particular concern about executions for crimes committed by children under 18. This was "strictly and unequivocally prohibited under international law."There had been a "staggering surge in the execution of at least 966 prisoners last year - the highest rate in over two decades," Shaheed told a news briefing."A large percentage of those executions are for drug offenses and under Iran's current drug laws, possession of 30 grams of heroine or cocaine would qualify for the death penalty. So there's a number of draconian laws," he said.Corruption and certain sexual activities can also qualify for the death sentence in the Islamic Republic, he added."The number of juvenile offenders executed between 2014 and 2015 - which is reportedly 16 - was higher than at any time during the past five years," Shaheed said.