Iran says it has foiled an online plot led by foreigners to spark dissent involving the tomb of Cyrus the Great on the day that many mark the birth of the Persian king by gathering at his grave.

The Iranian judiciary's news agency Mizan reported Sunday that the Intelligence Ministry disrupted plans for an "illegal gathering" in Pasargad, some 800 kilometers (500 miles) south of Tehran.

Roads to the area have been shut down over what authorities earlier described as an ongoing construction project. Online video purported to show fences earlier put up around the tomb. Iran's paramilitary Basij force was to hold a drill in the area.

Demonstrations there last year were claimed by a variety of anti-government forces abroad as a sign of unrest in Iran.