Some 450 people have been arrested in the Iranian capital over the past three days during unrest linked to protests, an official told local media on Tuesday.
"200 people were arrested on Saturday, 150 on Sunday and around 100 on Monday," Ali-Asghar Naserbakht, a deputy in the Tehran city governor's office, told the reformist-linked ILNA news agency.
Protests have been relatively small in Tehran compared with many parts of the country since the unrest began last Thursday.
"We feel the situation in Tehran is more calm than previous days. Already yesterday, it was calmer than before," said Naserbakht.
He added that no request had yet been put to the Revolutionary Guards to intervene in the capital.
"We will not permit insecurity to continue in any way in Tehran. If it continues, officials will take decisions to finish it," said Esmail Kowsari, a deputy commander for a local branch of the Revolutionary Guards, on state television.
Iranian state television has reported that nine people have been killed overnight amid the nationwide protests and unrest.
The report Tuesday puts the death toll in six days of demonstrations to at least 20 people.
State TV said six rioters were killed during an attack on a police station in the town of Qahdarijan. It reported that clashes were sparked by rioters who tried to steal guns from the police station.
State TV also said an 11-year-old boy and a 20-year-old man were killed in the town of Khomeinishahr, while a member of Iran's paramilitary Revolutionary Guard was killed in the town of Najafabad. It says all were shot by hunting rifles.
The towns are all in Iran's central Isfahan province, some 350 kilometers south of Tehran.
The European Union pushed Iran on Monday to guarantee the right to protest as authorities have moved to crack down on days of unrest across the nation.
Protests broke out Thursday and have quickly grown to become the biggest test for the regime since mass demonstrations in 2009.
"We have been in touch with the Iranian authorities and we expect that the right to peaceful demonstration and freedom of expression will be guaranteed," a spokeswoman for the bloc's foreign policy chief Federica Mogherini said in a statement.
"We will continue to monitor developments," the spokeswoman added.
The latest demonstrations on Monday came despite President Hassan Rouhani's vow that the nation would deal with "rioters and lawbreakers".
Authorities have confirmed more than 400 arrests since the outbreak of the unrest, of whom around 100 have been freed.
Rouhani came to power in 2013 promising to mend the economy and ease social tensions, but high living costs and a 12 percent unemployment rate have left many feeling that progress is too slow.