Fars did not identify the defendants but said one was accused of "moharebeh" — an Islamic term meaning warring against God — which carries the death penalty.
The others were accused of gathering with the intention of disrupting national security and propaganda activities against the Islamic establishment, Fars said.
Underlining the authorities' tough stand on dissent, national police chief Esmail Ahmadi-Moghaddam warned the opposition against using text messages or emails to organize fresh anti-government protests.
"Attending illegal gatherings, protests and insulting sanctities will be confronted," ISNA news agency quoted Ahmadi-Moghaddam as saying.
"These (emails and text messaging) … are completely under control. Users should not think that using proxies would prevent their identification," he added. It was his second public order this week to the opposition not to organize fresh protests.
Lacking newspapers, the opposition has in the past used the internet and other means of communication to spread the word about rallies.
POST-ELECTION PROTESTS
Protests began after Iran's disputed presidential election in June, which the pro-reform opposition says was rigged, a charge the authorities reject. For several weeks after the election, the use of mobile text messages seemed to be blocked.
In the worst violence since the post-election protests, eight people were killed on Ashura, the day of ritual Shi'ite mourning that fell on December 27, in clashes between security forces and supporters of opposition leader Mirhossein Mousavi.
The opposition website Rahesabz said earlier this month that more than 180 people, including 17 journalists, 10 Mousavi aides and some members of the outlawed Baha'i faith, were arrested after the Ashura day demonstrations.
Hardline clerics and authorities have called on the judiciary to punish opposition leaders for creating tension in Iran, saying they were "mohareb" (enemies of God).
"The files of 16 of the accused arrested on Ashura have been sent to Tehran's Revolutionary Court for consideration," Fars said, citing a court statement. "All the 16 are in detention. Their trial will begin soon," Fars added.
Last week, the official IRNA news agency said five detainees that Iran planned to put on trial in connection with the Ashura day protests were members of the armed People's Mujahideen Organization of Iran (PMOI).
The PMOI is an exile group opposed to Iran's Islamic system of government. Tehran's chief prosecutor has also said some members of the Baha'i faith were arrested over last month's protests.
Friday's Fars report did not make clear whether there were any alleged PMOI members or Baha'i followers among the 16 to be put on trial.
The June election plunged Iran into its worst internal crisis since the 1979 Islamic revolution and exposed deepening establishment divisions. Despite many arrests and an official crackdown, street protests have continued.
(Writing by Fredrik Dahl; editing by Tim Pearce)
