We'll slap your face, Iran warns UK

• Injured members of an Iranian security service shelter during anti-government protests in Tehran Picture: Getty Images

The Foreign Office said the ambassador, Simon Gass, had responded "robustly" to criticism of a British government statement calling on Tehran to respect the human rights of Iranian citizens.

Mr Gass, summoned to the Iranian foreign ministry, repeated Britain's position that the Iranian government must respect the human rights of its own citizens, the Foreign Office said.

On Monday, Foreign Secretary David Miliband criticised Iranian authorities after eight people were killed in anti-government protests.

Mr Mottaki threatened retaliation, adding: "If this country does not stop its prattling, it will receive a slap in its face."

Meanwhile, a representative of Iran's Supreme Leader, Ayatollah Ali Khamenei, said opposition leaders were "enemies of God" who should be executed.

"Those who are behind the current sedition in the country ... are mohareb (enemy of God] and the law is very clear about punishment of a mohareb," said cleric Abbas Vaez-Tabasi. Under Iran's Islamic Sharia law, the sentence for a "mohareb" is execution.

Earlier, it was claimed Iranian security forces were limiting the movements of a leading opposition figure by refusing to protect him when he leaves his home, as authorities broadened their crackdown with a new wave of arrests, including the sister of Nobel peace laureate Shirin Ebadi.

Iran's worst internal violence in three decades has worsened in the wake of clashes on Sunday that left at least eight people dead. Security forces also arrested a relative of opposition leader Mir Hossein Mousavi, while government supporters held rallies.

The son of leading opposition figure Mahdi Karroubi said his father no longer had security provided for him when he went out. Taghi Karroubi said this meant his father could not go outside safely, calling it a "quasi-house arrest".

Mr Karroubi and Mr Mousavi were the two defeated reformist candidates in the disputed 12 June presidential election.

The new arrests, along with tough criticism of Britain and the US, added to rising tensions with the West, which is threatening to impose tough new sanctions over Iran's nuclear programme.

Sunday's clashes were the worst since the aftermath of June's disputed presidential election. Opposition websites reported some ten new arrests on Monday, including Dr Noushin Ebadi.

Dr Ebadi, who won the 2003 Nobel Peace Prize for her human rights efforts in Iran, has stayed outside Iran since a day before the June elections. Speaking from London, she said she called her sister on Monday, and she was being punished because of the call.

"She was warned not to contact me. She is detained for the sake of me. She was neither politically active nor had a role in any rally."

Noushin Ebadi, a medical professor in Tehran, was arrested at her home on Monday and sent to prison, according to a statement issued by the Nobel laureate.

The opposition website Greenroad reported a series of additional arrests, among them Mr Mousavi's brother-in-law, Shapour Kazemi, and Mashallah Shamsolvaezin, a journalist who frequently criticises the government. Mr Mousavi's nephew was among those killed this week.

On Monday, US president Barack Obama praised "the courage and the conviction of the Iranian people" while condemning Iran's Islamic government for attacking demonstrators with "the iron fist of brutality".

US National Security Council chief of staff Denis McDonough also said the White House was reaching out to international partners to build support for sanctions against Iran. The sanctions are to punish Iran for its refusal to halt uranium enrichment.

The West suspects Iran is trying to build a nuclear bomb – a charge denied by Tehran.