Police Colonel Mehrdad Omidi, who heads the Internet crime unit, said the committee will fight "insults and the spreading of lies," terms widely used by the judiciary to describe opposition activities.
"Given the spread of Internet use, police must confront crimes taking place in the Web atmosphere," he said. "A special committee has been set up to monitor the Internet and deal with crimes ... such as fraud, ... insults and the spreading of lies."
Omidi specifically said the 12-member unit will intervene in "political matters on the Internet should there be an illegal act." The official said the unit will operate under the direction of the prosecution office.
Iranian authorities have banned most Web sites linked to Iran's opposition or those containing articles supporting the reform movement. The opposition has continued to set up new Web site within days of the old ones being blocked.
The opposition has no access to state media and has been promoting its message largely through the Internet.
Iranian newspapers are warned by authorities from time to time not to publish articles in support of the opposition leaders.
Iran's state radio and TV are directly controlled by Iran's Supreme Leader Ayatollah Ali Khamenei, who strongly endorsed President Mahmoud Ahmadinejad's re-election in June. The opposition maintains the contest was marred by fraud.
It was not immediately clear exactly how the new unit would carry out its surveillance.
Reform-minded journalist Akbar Montajabi described this as the latest set of restrictions being imposed on the media in Iran.