Leaders of Iran’s opposition movement and the country’s hard-line establishment sharpened their months-long confrontation Saturday, with opponents calling on demonstrators to take to the streets on a highly charged anniversary next week and the judiciary putting 16 alleged protesters on trial.

Opposition leaders Mir-Hossein Mousavi and Mehdi Karroubi voiced deep sorrow over the “hasty” executions of two Iranians hanged last week in a move widely interpreted as an attempt at intimidation ahead of anticipated confrontations Feb. 11, the 31st anniversary of the 1979 founding of the Islamic Republic.

Their “invitation” for supporters to take to the streets showed fresh daring. Neither had explicitly called for protests on the Dec. 27 Shiite Muslim holiday of Ashura, the last round of confrontations between security forces and demonstrators.

It came as top officials warned of consequences for anyone who tries to take part in anything but official rallies on the anniversary, traditionally an occasion for anti-U.S. and anti-Israeli slogans and imagery.

“Anyone breaking ranks with the Iranian people will be considered an agent of foreigners,” Brig. Gen. Hossein Hamedani, the Tehran Revolutionary Guard commander, told SepahNews, the website of the elite military branch. “Any voice or color other than the voice of the Islamic Revolution will be pushed aside, and if a minority makes such an attempt, it will be firmly confronted.”

Another Revolutionary Guard officer, Gen. Ali-Mohammad Naini, told the Fars news agency that authorities planned to double the number of government supporters at this year’s rally, presumably by busing them in from the provinces and providing them with pay and food.

Meanwhile, 16 alleged opposition supporters, two of them women, were brought to trial Saturday on charges of plotting against the Islamic government and being in cahoots with foreign enemies of Iran.

According to prosecutors, all 16 had confessed to espionage and taking part in “counter-revolutionary” gatherings with the aim of carrying out bombings and assassinations, distributing leaflets, burning property and writing graffiti.

Many considered the televised trial an attempt to cow potential protesters into staying home Feb. 11. But months of similar trials and a continuous stream of dire warnings against the opposition have failed to subdue a grass-roots movement unlike any Iran has experienced.