They were reportedly joined by opposition supporters who had also gone to the cemetery to pay their respect to "the martyrs of the Green opposition."
One man who lost his uncle in the crackdown told RFE/RL's Radio Farda that the cemetery was filled with more than 200 security agents. He said a number of plainclothes agents were sitting at Neda Agha Soltan's grave and wouldn't let anyone approach to pray for her soul. He said the security forces were particularly sensitive about Neda's grave.
Another witness told Radio Farda that she saw clashes between the police forces and opposition members who refused to leave the cemetery.
Blogger "Saze Mokhalef" also writes that whenever someone would get close to Neda's grave to pray for her, security agents would use force and insult them and force them to leave.
The blogger says the Iranian government is even afraid of gravestones. "Imagine your work is [to sit] at the grave of Neda and not let anyone come there to pray! How dishonorable can you be?"
The "Tahavolesabz" website has posted some March 18 pictures of the graves of Neda and also Ashkan Sohrabi and Said Abbasi, who were also killed in the postelection crackdown.
Some opposition members have said that they will put the pictures of some of the "martyrs" at their traditional "haft sin" table that is set to mark the Iranian New Year.
According to the opposition, more than 72 people were killed in the crackdown that followed last year's disputed presidential vote.