"The Interior Ministry will confront seditionists and sedition leaders in accordance with the law," Interior Minister Mostafa Mohammed Najjar told reporters Saturday.
Najjar claimed it was elements of the opposition forces who started shooting at members of the public and police during protests in Tehran Monday to foment chaos that led to two people being killed and several wounded, the semi-official Iranian news agency Fars reported.
Najjar said members of the Iraqi opposition group Mujahedin Khalq had entered the country and planned to shoot at protesters attending the mass rally to mark the deaths of two protesters killed by security forces in anti-government demonstrations last week, the news agency said.
Plans by opposition leaders to conduct a demonstration Sunday came days after Iranian lawmakers called for the execution of leaders Mir Hossein Mousavi and Mahdi Karroubi and organized pro-government rallies on Friday to denounce the two.
"In response to the brutal suppression and the killing of the supporters of the Green Movement, we will go out in streets in major squares (of Tehran and other big cities) ion Sunday, which will mark the seventh day after the deaths of our martyrs," Mousavi's official Web site Kaleme.org said.
Last week Mousavi and Karroubi were placed under house arrest, and have since been totally isolated from events.
"They are both placed under house arrest, there's no information on their situation and health. The road to Mousavi's house is blocked by security forces who have not given permission to anybody to visit him for the past whole week, including his daughters. They are both denied access to the outside world," Ardeshir Amir-Arjomand, a spokesman for the two opposition leaders, told the British newspaper The Observer.
He expressed concern for Mousavi's health, saying "he is given food by the security officials and we don't have any knowledge of what they are providing him with."