Iran's army warned on Friday that it would "confront the enemies" to ensure security and peace in the country, according to a statement, as protests rage over the death of a woman in the morality police's custody.
Iranians have staged nationwide demonstrations over the case of Mahsa Amini, 22, who died last week after being arrested for wearing "unsuitable attire".
The army said "these desperate actions are part of the evil strategy of the enemy to weaken the Islamic regime".
Pro-government protests were planned for Friday, Iranian media said.
Protesters in Tehran and other cities have torched police stations and vehicles as outrage over Amini's death showed no signs of abating, with reports of security forces coming under attack.
Amini's death has reignited anger over issues including restrictions on personal freedoms in Iran - including strict dress codes for women - and an economy reeling from sanctions.
Iran's clerical rulers fear a revival of the 2019 protests that erupted over gasoline price rises, the bloodiest in the Islamic Republic's history.