There are reports of protests breaking out in Iran for a fifth day, despite a statement from the president that the unrest "is nothing".
Anti-government chanting and burning cars were reported as night fell in the capital, Tehran, while police said an officer was killed in a central city.
President Hassan Rouhani said protests were an "opportunity, not a threat" but vowed to crack down on "lawbreakers".
The US meanwhile stepped up support for the protesters' "bold resistance".
The protests began last Thursday in the city of Mashhad, initially against price rises and corruption but now with wider anti-government sentiment.
The latest reports speak of a heavy police presence in the capital.
Initially, state TV said that 10 people had been killed overnight, but that figure was later raised to 13 by a regional governor:
Six died after shots were fired in the western town of Tuyserkan, 300km (185 miles) south-west of Tehran
Later, Hamadan province's governor told the ISNA agency that another three people had also been killed in the city
Two people died in the south-western town of Izeh, an official said
Two died in clashes in Dorud in Lorestan province
Two people also died in earlier violence, reports BBC..