There was a heavy police presence in Tehran as small groups of protesters ran through the city centre shouting anti-regime slogans, local agencies reported.
Some arrests were made before calm returned to the capital, reports said.
State television said one policeman had been killed and three others wounded by fire from hunting rifles in the city of Najafabad in central Iran.
The latest demonstrations came despite President Hassan Rouhani´s vow that the nation would deal with “rioters and lawbreakers”.
Media cited Ali Shamkhani, secretary of Iran´s Supreme National Security Council, as blaming the violence on social media.
“Hashtags and messages about the situation in Iran come from the United States, Britain and Saudi Arabia,” he said.
“What is happening on social networks concerning the situation in the country is a proxy war against the Iranian people.”
Germany calls for calm in Iran, urges respect for right to protest
US President Donald Trump, who has repeatedly criticised Tehran over four days of demonstrations, said it was “time for a change” and that Iran´s people were “hungry” for freedom.
The intelligence ministry released a statement saying “rioters and instigators” have been identified “and will be dealt with seriously soon”.
The Revolutionary Guards published photos of three wanted people and called on the public to report any “seditionist elements”.
#Iran, Dec 30, 2017 – Third day of Public protest against high prices In this clip on the main entrance of the #Tehran University , students are chanting slogan: “ #Khamenei shame on you, let go the country” #FreeIran #RegimeChange #Iranprotests
Nine people were killed overnight as protests across Iran entered a sixth day, AP reported citing Iranian state television, adding that all victims had been shot with hunting rifles.
Iranian state TV, said, that at least 10 people had been killed in the nationwide unrest. Over 400 people have reportedly been arrested following the protests, according to AFP data from Sunday.
Six protesters were among those killed in the town of Qahdarijan on Monday night, the state TV said, adding that the rioters had attempted to steal guns from the police station. Also an 11-year-old boy and a 20-year-old man were killed in the town of Khomeinishahr. The ninth fatality was a member of Iran’s paramilitary Revolutionary Guard in the town of Najafabad.
Monday, Iranian President Hassan Rouhani said that the protests may have been partially stirred up by external forces interested in destabilizing the country. “The enemies of the Islamic Republic of Iran are angry with the glory, success, and the progress of the Iranian nation; and they have vowed to bring the regional troubles to Iran,” he said, according to the Mehr news agency.
The overall death toll after six days of unrest has reached 20 people, according to state TV.
Pro- and anti-government demonstrations have been taking place in Iran since Thursday. Economic hardship and alleged corruption mostly prompted the anti-government rallies.