Iranian President Mahmoud Ahmadinejad Monday called his opponents enemies of Iran and agents of foreign countries, the ILNA news agency reported.
"The enemies of the Iranian nation are now frustrated and want to take revenge through insulting the country's sanctities," Ahmadinejad said, DPA reported.
The supporters of opposition leaders Mir-Hossein Moussavi and Mehdi Karroubi are accused by clergy of burning pictures of Grand Ayatollah Ruhollah Khomeini, the late leader of the 1979 Islamic revolution, and his successor, Ayatollah Ali Khamenei, during rallies last Monday.
"The enemies should fear the typhoon of the Iranian people's anger," the president warned.
Moussavi, who was prime minister during the Khomeini era, expressed doubt that his supporters - the Green Movement - would have committed such acts. The colour green is a symbol for protest and change in the current political debate.
Green Movement student supporters on Sunday staged demonstrations at several universities in Tehran and, while carrying Khomeini's pictures, denied the charges and said the accusations were fabricated propaganda by state television.
Ahmadinejad said that the latest move by the opposition clearly proved that its leaders were "against the nation and were agents of foreigners."
There had been speculation on opposition websites Saturday night that following the recent protests leading opposition members, including Moussavi himself, might be arrested.
Opposition supporters also warned they would gather in large numbers to protest in Tehran if arrests were carried out.
Khamenei, who according to the constitution has the final say on all state affairs, however, called on the people to remain calm and allow the judiciary to deal with the offenders.
The political turbulence in Iran began after the disputed June 12 presidential polls which led to Ahmadinejad's re-election.
The opposition accused Ahmadinejad of election fraud and its supporters have since staged several protests, the latest on December 7.