German Foreign Minister Annalena Baerbock on Monday summoned Iran's ambassador to Berlin for the second time in a week over a rash of executions by Tehran, her spokesman said.
The spokesman, Christofer Burger, confirmed the move when asked about reports the envoy had been summoned "over massive human rights violations and a wave of executions".
Iran said Saturday it had executed a British-Iranian dual national sentenced to death for spying for the United Kingdom, drawing strong condemnation from Western governments and international rights groups.
Alireza Akbari, 61, was hanged after being convicted of "corruption on earth and harming the country's internal and external security by passing on intelligence", the judiciary's Mizan Online website said.
Mizan said Mr. Akbari, who had been arrested more than two years ago, had been a spy for Britain's MI6 secret intelligence agency and had received around $2 million for his services.
British Prime Minister Rishi Sunak said he was "appalled" by the execution.
Iran summoned the British ambassador to protest against what it described as "unconventional interventions", after Britain said it would summon Tehran's envoy.
French President Emmanuel Macron denounced a "heinous and barbaric act" by Tehran.
Mr. Akbari, a veteran of the 1980-88 Iran-Iraq war, was arrested between March 2019 and March 2020, state media said.
He was once identified by the government's official Iran newspaper as a former deputy defence minister under Ali Shamkhani, who currently heads Iran's Supreme National Security Council.
Mr. Akbari had also been an adviser to the navy commander and headed a division at the defence ministry's research centre, state media said.
Amnesty International says Iran is the world's most prolific user of the death penalty after China.
Iran has been rocked by protests that erupted over the September 16 death of Mahsa Amini, a 22-year-old Iranian Kurd, after her arrest for an alleged breach of the country's dress code for women.
Eighteen people have been sentenced to death in connection with the protests, according to a count compiled by AFP from official announcements. Four of them have been executed.
Germany and France last Monday summoned Iran's respective envoys in protest against Tehran's deadly crackdown on the demonstrations and the latest executions of anti-government protesters.