Two people, one a teenage boy, died after being run over by a fire engine stolen by protesters in the town of Dorud, state media said. Two other people were shot dead at the weekend in the town, which has been a flashpoint for protests.
Iran's Government claimed that armed demonstrators had tried to seize control of police stations and military bases.
There was no independent confirmation but videos on social media purported to show men ransacking a Revolutionary Guard office and pulling down a picture of Ayatollah Khomeini, the founder of the Islamic Republic.
In the largely Kurdish city of Kermanshah, a crowd overpowered a pro-government Basij militiaman and stripped him of his trousers, sending him stumbling, humiliated, into the cold night.
The protests began on Friday as a narrow demonstration over rising food prices, but quickly spiralled into the gravest challenge to Iran's theocratic government since 2009, when millions took to the streets over election results.
Hassan Rouhani, Iran's President, has tried to strike a balance between acknowledging some of the protesters' grievances while also warning that the Government would crack down on unrest.
The protests "may seem to be a threat, but it can be turned into an opportunity to see what the problem is," Rouhani said.
While Rouhani's hardline opponents initially appeared encouraged by the discontent with his economic policies, they were caught off guard as the unrest took aim at the core pillars of the Islamic Republic, including Ayatollah Khamenei, the Supreme Leader.
Sigmar Gabriel, Germany's Foreign Minister called on Iran "to respect the rights of the demonstrators to assemble and to peacefully raise their voices".