The United Kingdom’s government has formally summoned Iran’s ambassador to London to protest what Britain’s foreign secretary described as the “horrendous and brutal killing” of demonstrators amid a nationwide crackdown on anti-government protests.

The move reflects growing alarm in Western capitals about the scale of the violence in Iran, where protests that began in late December over economic distress have broadened into widespread calls for political change and have been met with intense force by security services.

Speaking in the House of Commons, Foreign Secretary Yvette Cooper said the British government had summoned Ambassador Seyed Ali Mousavi to “underline the gravity of this moment” and to demand that Iranian authorities answer for reports of mass casualties and repression.

She condemned the violence “in the strongest of terms” and urged Iran to respect fundamental rights and freedoms.

Recent reports from within Iran suggest the death toll may be significantly higher than official figures indicate, although precise numbers remain difficult to verify due to communications shutdowns imposed by the authorities.

In addition to the diplomatic summons, Ms Cooper outlined plans to introduce legislation to implement “full and further sanctions” targeting key sectors of the Iranian economy, including finance, energy, transport and software.

These measures are intended to increase pressure on Tehran’s leadership in response to what Britain characterises as excessive use of force against civilians.

She said British officials had also been in contact with Tehran’s foreign minister to convey London’s objections directly.

The United Kingdom’s action follows similar diplomatic pressure from other European states, which have also summoned Iranian envoys and criticised Tehran’s handling of the unrest.

The European Union and several member states are coordinating additional punitive measures and have called for accountability for those responsible for the violence.

Within Iran, authorities have attributed the unrest to foreign interference and labelled protesters as criminals, a narrative rejected by Western governments.

The crisis has drawn sustained international attention as Iranians continue to protest under challenging conditions, and as Western governments weigh further sanctions and diplomatic actions.

The United Kingdom’s decision to summon Iran’s ambassador underscores London’s commitment to confronting what it sees as grave human rights violations and to supporting broader international efforts to address the situation in Tehran and across the region.