An Iranian opposition website said on Thursday the government was moving troops and armoured military vehicles to the capital on the day supporters of opposition leader Mirhossein Mousavi planned to hold a rally.
"Hundreds of military forces and tens of armoured vehicles ... are moving towards Tehran. Some of the vehicles are used for suppressing street riots," the Jaras website said.
The report could not be confirmed independently by Reuters.
Jaras also said security forces had a heavy presence in various Tehran squares ahead of the planned opposition rally.
Iran's police chief warned supporters of Mousavi on Wednesday of harsh treatment if they joined illegal anti-government rallies.
In Iran's bloodiest unrest since the aftermath of the disputed June 12 presidential election, eight people were killed on Sunday and at least 20 pro-reform figures, including three senior advisers to Mousavi, were arrested.
The government reacted by organising demonstrations, starting on Monday, in which hundreds of thousands of people took part. Demonstrators called for the execution of the opposition leaders, Mousavi and moderate defeated presidential candidate Mehdi Karoubi.
Concern over political unrest in Iran helped push oil prices briefly above $79 a barrel to fresh five-week highs on Tuesday and they held near that level on Wednesday.
