Iranian authorities on Sunday prevented an "illegal gathering" at the tomb of ancient Persian king Cyrus the Great and arrested a number of suspects, local media reported.
The Mizanonline news website said the intelligence ministry had identified members of "a counter-revolutionary group which had wanted to organise an illegal gathering under the pretext of celebrating Cyrus".
Authorities on Saturday cut the main highway between the cities of Shiraz and Esfahan, which leads to an archaeological site where the tomb is believed to be located.
They said the closure was for road work.
Semi-official ISNA news agency reported that the head of the elite Revolutionary Guard, General Hashem Ghiassi, had issued a warning Saturday to the "counter-revolutionaries".
Authorities in Iran last October arrested several organisers of a rally at the same site.
Footage posted on social media showed participants chanting for freedom of expression, along with nationalistic and anti-Arab slogans.
Authorities later said they had arrested a number of rally organisers "for having violated norms and chanting slogans against the values" of the Islamic republic of Iran.
Cyrus the Great was the founder of the Achaemenid Empire in the 6th century BC and ruled over ancient Persia for about 30 years.
So-called "Cyprus Day" rallies are held on October 29 to mark the king's capture of Babylon in 539 B.C, after which he allowed Jews held there as slaves to walk free.
Iran's last shah Mohammad Reza Pahlavi, who was ousted by the 1979 Islamic revolution, had claimed to be a descendent of Cyrus.