Armed protesters tried to overrun military bases and police stations in Iran before security forces repelled them, killing 10 people, state television has reported.
Iran’s semi-official Mehr news agency said an assailant using a hunting rifle killed a policeman and wounded three other officers during a demonstration in the central city of Najafabad, about 200 miles south of Tehran.
It was the first report of a police officer dying during five days of unrest and raised the death toll to at least 13.
The demonstrations, the largest to strike Iran since its disputed 2009 presidential election, began on Thursday in Mashhad over economic issues and have expanded to several cities, with some protesters chanting against the government and the supreme leader Ayatollah Ali Khamenei.
Hundreds of people have been arrested.
Iranian state television aired footage of a ransacked private bank, broken windows, overturned cars and a fire engine that appeared to have been set ablaze.
It said 10 people were killed by security forces during clashes on Sunday night.
In a later report, state TV said six people were killed in the western town of Tuyserkan, 185 miles south-west of Tehran, and three in the town of Shahinshahr, 195 miles south of Tehran. It did not say where the 10th person was killed.
Earlier on Monday, the semi-official ILNA news agency quoted Hedayatollah Khademi, a representative for the town of Izeh, as saying two people died there on Sunday night.
He said the cause of death was not immediately known, though authorities later described one of the deaths as the result of a personal dispute.
Two protesters also were killed during clashes late on Saturday in Doroud, some 200 miles south-west of Tehran in Lorestan province, authorities have said.
On Sunday, Iran blocked access to Instagram and the popular messaging app Telegram used by activists to organise.
President Hassan Rouhani acknowledged the public’s anger over the Islamic Republic’s flagging economy, though he and others warned the government would not hesitate to crack down on those it considers lawbreakers.
Mr Rouhani also stressed Iran “has seen many similar events and passed them easily”.
US President Donald Trump, who has been tweeting in support of the protesters, continued into the new year, describing Iran as “failing at every level despite the terrible deal made with them by the Obama Administration”.
“The great Iranian people have been repressed for many years,” he wrote.
“They are hungry for food & for freedom. Along with human rights, the wealth of Iran is being looted. TIME FOR CHANGE!”
The Iranian regime tries desperately to sow hate between Iranians and Israelis. They won't succeed. When this regime finally falls – and one day it will – Iranians and Israelis will be great friends once again. I wish the Iranian people success in their noble quest for freedom. pic.twitter.com/kk8wTYmhnz
— Benjamin Netanyahu (@netanyahu) January 1, 2018
Israeli Prime Minister Benjamin Netanyahu, calling the protesters “brave” and “heroic,” said in a video posted to YouTube on Monday that the protesters sought freedom, justice and “the basic liberties that have been denied to them for decades”.
Iran’s economy has improved since its 2015 nuclear deal with world powers, which saw the country agree to limit its enrichment of uranium in exchange for the end of some international sanctions.
Tehran now sells its oil on the global market and has signed deals to purchase tens of billions of dollars’ worth of western aircraft.
That improvement has not reached the average Iranian, however.
Unemployment remains high and official inflation has crept up to 10% again.
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