Iran says it has executed a prisoner arrested during the ongoing anti-government protests – the first known death sentence linked to the unrest.

The execution on Thursday came after people are believed to have gathered around Azadi Square in the capital Tehran overnight.

The prisoner has been identified as Mohsen Shekari by the Mizan news agency, which is run by the country’s judiciary.

He was accused of injuring a security guard with a machete and blocking a street in Tehran, according to the semi-official Tasnim news agency.

Amnesty International has criticised what it describes as “sham trials designed to intimidate those participating in the popular uprising that has rocked Iran”.

State media published a video of what it said was Shekari’s confession where he appears with a bruise on his right cheek.

He admitted to striking a member of the Basij militia with a knife and to blocking a road with his motorbike alongside one of his friends.

Rights groups have said Shekari was tortured and forced to confess to his crime.

The organisation says Iranian authorities are seeking the death penalty for at least 21 people.

The execution was condemned by UK foreign secretary James Cleverly, who said he was “outraged”.

He said on Twitter: “The world cannot turn a blind eye to the abhorrent violence committed by the Iranian regime against its own people.”

The execution comes as protesters continue to take to the streets in defiance of the government and the threat of the security forces, following the death of Mahsa Amini.

The 22-year-old Kurdish-Iranian woman died while in the custody of Iran’s morality police.

Videos on social media appear to show a crowd chanting “Do not call me a seditionist. You are the sedition, the oppressor” as they gathered in Tehran on Wednesday night.

The arch of the Azadi Tower Museum can be seen in the background as people clapped and shouted by the side of the road.

Confronted with perhaps the greatest threat to its rule in decades, the regime has responded to the protests with a brutal crackdown that has seen at least 475 protesters killed, according to the activist HRANA news agency.

Iran has blamed the unrest on its foreign foes as well as Kurdish separatists, but its claims have been criticised by academics.

This week, the sister of Supreme Leader Ayatollah Ali Khamenei condemned the crackdown and called on the Revolutionary Guards to lay down their weapons.