Stefano Sannino, secretary-general of the European External Action Service (EEAS), reiterated the EU's outrage to the ambassador, Hossein Dehghani, the EEAS said in a statement. 

Sannino also repeated an EU call on Iranian authorities to annul without delay death sentences already pronounced against other protesters.

Earlier on Monday, the UK and France summoned Iran’s most senior diplomats in their respective countries after executions over the weekend and the ongoing violent crackdown on protesters in the country.

Britain's foreign minister James Cleverly summoned the chargé d’affaires after Iranian authorities executed protestors Mohammad Mahdi Karami and Seyyed Mohammad Hosseini. 

"Today I have summoned the Iranian Chargé d’Affaires to condemn in the strongest possible terms the abhorrent executions we witnessed over the weekend," Cleverly said in a statement. 

The French foreign ministry said on Twitter: "He (the chargé d'affaires) was informed of our strongest condemnation of the executions and repression in Iran." 

It added that Paris had already voiced this point several times to the Iranian authorities. 

Since the death of 22-year-old Kurdish Iranian woman Mahsa Amini last September, Britain said it had imposed more than 40 sanctions on leading officials in Iran "for their role in serious human rights violations." 

The two men were hanged on Saturday for allegedly killing a member of the security forces during protests that followed the death of Amini. 

The latest execution brings the number of protesters officially known to have been executed since the unrest to four.