Arman Abdolali, 25, was executed on November 24 over the alleged killing of his girlfriend, despite international appeals for his life to be spared.

The UN Human Rights Office called the execution "deeply alarming and shocking,” while the nongovernmental organization Iran Human Rights (IHR) described it as “an international crime."

Speaking hours after Abdolali’s hanging, his father, Kamiar, told RFE/RL: "This kid was not a murderer. He shouted until the last minute that he's not a murderer."

"This kid begged for a last meeting, but they didn't allow it. He said he couldn't meet his younger brother. Others who were executed had a last meeting two days before their execution," he said.

The EU condemned the execution "in the strongest terms," saying it violated international treaties, while the UN Human Rights Office called it "deeply alarming and shocking,” and the nongovernmental organization Iran Human Rights (IHR) described it as “an international crime."

"Death sentences for crimes committed by persons below the age of 18 are contrary to international obligations under the International Covenant for Civil and Political Rights and the Convention on the Rights of the Child," a spokesperson for EU foreign policy chief Josep Borrell said in a statement, adding that Iran is a party to both.

Abdolali’s girlfriend went missing in 2014 and her body has never been found.

The Oslo-based IHR said Abdolali confessed to the murder at the time of his arrest, but later withdrew the confession.

Amnesty International has called his trial "grossly unfair" by a court that "relied on torture-tainted 'confessions.'"

His execution had been postponed several times after rights groups warned that it would violate international conventions that Iran has signed that prohibit the execution of minors.

According to Amnesty International, Iran executed at least 246 people last year -- retaining its place as the most prolific user of capital punishment in the region and the second worldwide after China.

IHR, which monitors the use of the death penalty in Iran, said at least 64 juvenile offenders have been executed in Iran over the past 10 years.

"Besides being executed for an alleged offense committed at under 18 years of age, which is a violation of international law, Arman was sentenced to death based on confessions extracted under torture, without a fair trial and due process," said IHR Director Mahmud Amiry-Moghaddam.

A spokeswoman for the UN Human Rights Office noted that Abdolali’s hanging went ahead “despite interventions by numerous parties" that included direct contact between the UN and Iran.

"We also deplore that over the last two months Abdolali had been transferred to solitary confinement six times ahead of his scheduled execution, postponed on each occasion before going ahead," the spokeswoman said, adding that the "repeated transfers for execution and then returning him without any explanation" constituted "psychological torture."

Late on November 23, Amnesty International urged Iran's Supreme Leader Ayatollah Ali Khamenei to immediately halt Abdolali’s planned execution.

“We are outraged to learn that despite a global outcry the…authorities suddenly transferred Arman Abolali to solitary confinement this evening and told his family that he is due to be executed in a few hours,” the London-based human rights watchdog tweeted.

With reporting by AFP and ISNA