Iranian security forces drive through a street in Tehran, 27 December 2009
Eyewitnesses in Tehran say Iranian police have fired on protesters during the Shia festival of Ashura. At least four people are reported to have been killed during Sunday's clashes in the capital.
This man told BBC Persian TV what he saw.
The guards came from the other side of Hafez bridge [in central Tehran]. They parked their cars and walked towards us. They were firing tear gas directly into the crowds and charging at them.
People turned and threw stones at them. The clashes were in full swing, people surged forward and cornered the guards around a nearby bank and set fire to their motorbikes.
The atmosphere was very tense, there was smoke and fire.
He shot five bullets and one hit the man next to me
We could hear gunshots. Then, we saw three people being shot. I saw that happen with my own eyes.
One was shot in the head, and then another two people were hit in the body. People chased the guards away and lifted those who were shot into cars. The cars drove off, I don't know where they went.
At this stage, people were getting very angry and anxious. They started crying and chanting even more radical slogans, cursing the officials.
It was at that point the Basij [militia] forces came from the other side of the Hafez Bridge. People charged at them, the Basij retreated but one of them left his motorbike behind, so he came back to get it.
He was 18 or 19 years old and he was armed with a gun. He started shooting at us, it was horrifying to see.
He shot five bullets and one of them hit the man next to me, on his right side.
There was a black car nearby, so we bundled him into that.
People took the other injured people away from the scene, to surrounding houses, or to adjoining streets.
Translated by BBC Persian TV