The statement followed a pair of attacks on Iranian parliament and the holy shrine of late Imam Khomeini in Tehran.
Iran has arrested nearly 50 people in connection with twin attacks on Tehran that killed 17 people last week, officials said, as security forces stepped up efforts to crack down on suspected militants.
On Saturday, intelligence minister Mahmoud Alavi said the alleged mastermind behind the attacks had been tracked down and killed outside the country.
On Sunday, the head of the justice department in Kordestan province in western Iran announced more arrests.
The terrorist attacks - the first in many years on Iranian soil - have been claimed by the jihadist group Islamic State in Iraq and Syria (Isis), which has denounced Shia Iran as a nation of heretics in the past.
"The terrorists first went by auto to the mausoleum and after dropping two of them off, went to the city centre to attack parliament", the police said.
"The mastermind who controlled the team. who had fled outside the country. paid the price for his crimes, with the cooperation of intelligence services of allied countries", Mr Alavi told state television. "America's claim of fighting against Islamic State is a lie", Khamenei said in a meeting with high-ranking Iranian officials, according to his official website.Iran and the United States cut diplomatic ties shortly after Iran's 1979 Islamic revolution and enmity to Washington has always been a rallying point for hardline supporters of Khamenei in Iran.Khamenei has made several statements denouncing the United States since the start of the Muslim holy month of Ramadan, while U.S. President Donald Trump has spoken out against Iran in harsh terms since taking office, indicating that he will reverse the previous administration's attempts at rapprochement with Tehran.
We possess documents and information showing the direct supports by the USA imperialism for this highly disgusting stream [IS] in the region which has destroyed the Islamic countries and created a wave of massacres and clashes, Fars news agency quoted Izadi as saying.
In 1981, a bomb planted by an Iranian opposition group in Tehran killed 27 Iranian members of parliament and dozens of other officials.
Iranian lawmakers said the intelligence minister had assured them that "all Islamic state elements have been eliminated" in the country.