A representative of Iran's supreme leader has said opposition leaders are "enemies of God" who should be executed under the country's laws.
The comments by Abbas Vaez-Tabasi, the representative of Ayatollah Ali Khamenei, coincided with demonstrations by thousands of government supporters on Tuesday.
"Those who are behind the current sedition in the country ... are mohareb [enemies of God] and the law is very clear about punishment of a mohareb," Vaez-Tabasi said on state television.
At the pro-government rallies, which follow days of protests by opposition supporters, demonstrators also called for opposition leaders to be punished for fomenting unrest after June's disputed presidential election, state media reported.
The reports stated that the demonstrations had taken place spontaneously.
Iran's government has blamed the unrest on foreign influences, including Britain, the US and Israel.
Earlier, Iran called on the British ambassador to respond to accusations over the UK government's "interference" in Iran's domestic affairs.
"If Britain does not stop talking nonsense it will get a slap in the mouth"
Iran's foreign minister
"If Britain does not stop talking nonsense it will get a slap in the mouth," Manouchehr Mottaki, the Iranian foreign minister, told a news conference.
The summons came hours after the Revolutionary Guards security force said opposition groups were working with Tehran's foreign enemies, implicating London.
The UK said that its envoy would be robust in the face of any Iranian criticism and reiterate that Tehran must respect human rights.
Meanwhile, Ali Larijani, Iran's parliamentary speaker, challenged the calls from Barack Obama, the US president, for Tehran to respect the protesters' rights ,saying the US should be more concerned about "the behaviour of his troops in Guantanamo, Abu Ghraib, Afghanistan and Iraq".
"Your admiration for the opposition movement protesters will ruin your reputation and will also reveal where the movement of this anti-religious group is linked to," he said, reading from a statement prepared on behalf of the Iranian parliament.
Karim Sadjadpour, an Iran analyst at the Washington-based think-tank the Carnegie Endowment for International Peace, told Al Jazeera the West was facing a "delicate situation" in Iran.
"On one hand the United States and European countries should continue to condemn human rights abuses in Iran - they should want to be on the right side of history when they see people courageously struggling for democratic change," he said.
"On the other hand, this is an internal Iranian drama which is unfolding and they don't want to walk into a trap of tainting the independence of the opposition movement."
Eight people were killed in the latest anti-government protests which coincided with the marking of Ashoura, Shia Islam's holiest event.
Hundreds of people were arrested as fierce battles were fought on the streets of Tehran and many more have reportedly been detained since, including aides to opposition leaders and pro-reform clerics.
Shirin Ebadi, the country's Nobel prize-winning human rights activist, said that her sister was among those arrested.
Sadjadpour said Iran's government "hasn't ceded one inch" to the opposition movement and was unlikely to do so any time soon.
"Since June [when the post-election unrest began] any moderate or pragmatic elements that were in the Iranian system have essentially been purged from the decision-making structure," he told Al Jazeera.
"You now have a very hardline government whose colour spectrum ranges from pitch black to dark grey. They are unified in wanting to preserve the regime."
'Peaceful and law-abiding'
Iran's primary reformist party criticised the government for not respecting Iranian law in tackling the opposition protesters.
|Iran's response to the opposition protests has
earned it international criticism [EPA]
"The Green Movement is peaceful and law-abiding. It avoids any violence and will press ahead on its path," the Islamic Iran Participation Front (IIPF) said in a statement carried by an opposition website.
"The IIPF condemns attacks on defenceless people and believes the incidents after the presidential election and especially on Ashoura indicate the complete failure of the coup d'etat and not the strength of government."
Fatemeh Haghighatjoo, a former member of the Iranian parliament, told Al Jazeera that the government faced a fundamental crisis.
"They can't control the events so they made the Ashoura incidents as a scenario that could give [them] enough confidence to crack down on the [Green] Movement," she said from Massachusetts in the United States.
"They think that if they could use more violence, they can stop the movement ... if this strategy continues I think we could see the collapse of the government.
"There is a real threat for arresting the [opposition] leaders such as [Mir Hossein] Mousavi, [Mohammad] Khatami and [Mehdi] Karroubi in future days."