As the Iranian government prepares to make sensitive cuts to subsidies, police have been sent on to streets of Tehran.
President Mahmoud Ahmadinejad said cuts of energy and food subsidies would start from Sunday.
Under the new system, each car would receive 60 litres of fuel per month at a subsidized price of 40 cents per litre, a four-fold increase. Further gasoline purchased would cost 70 cents a litre, compared to the current price of 40 cents.
In 2007, angry protesters set dozens of gas stations on fire after the system of fuel rationing was implemented and it appears the government fear similar scenes when the cuts come into effect.
Witnesses say clusters of riot police could be seen at every major square in the city. There has been no official explanation or report of disorder so far.