Iran hanged 10 people convicted of drug trafficking on Monday, the semi-official Mehr news agency reported, part of what rights group Amnesty International called a "state killing spree".
Executions are regular events in Tehran, and the latest took place in a prison in the capital. The judiciary said those hanged were members of two drug smuggling gangs, Mehr said.
Iran invariably dismisses criticism from Western human rights groups over its high rate of executions, saying it is implementing Islamic law and responding to a major drugs problem.
Last week, Amnesty urged Iranian authorities to commute all death sentences and remove the penalty as a possible punishment. The London-based human rights watchdog said in a statement it believed 344 people had been executed in Iran since March.
Iran is a transit route for narcotics smuggled from neighbouring Afghanistan, which produces more than 90 percent of the world's opium, the raw ingredient of heroin.
According to the country's media, more than 3,500 Iranian soldiers have been killed in clashes with drug smugglers since the 1979 Islamic revolution.
Among those executed on Monday was Saeed Sedighi, who Amnesty said "appears to have had no opportunity to appeal against his conviction and sentence".
In a statement later on Monday Amnesty condemned the executions, saying they were part of a "state killing spree".
"While Iran's security forces have a right to prosecute individuals for offences connected to the production and supply of illegal drugs, drugs offences do not meet the threshold of 'most serious crimes' to which the death penalty must be restricted under international law," Amnesty's statement said.
Murder, adultery, rape, armed robbery, drug trafficking and apostasy - the renouncing of Islam - are all punishable by death under the Islamic judicial code that Iran adopted after the revolution.