Iranian security forces have opened fire on crowds near Tehran marking the 40th day of mourning for a woman shot dead while protesting, witnesses say. 

Authorities shut a cemetery and blocked roads to stop people reaching the grave of Hadis Najafi, who has become a symbol of the unrest engulfing Iran.

Videos showed thousands walking along a highway to reach the cemetery in Karaj and shouting anti-government slogans.

Security personnel responded by firing live rounds, witnesses told the BBC.

Officers in plainclothes also attacked people with machetes, they added.

A gunshot could also be heard in a video from the area near the cemetery that has been verified by BBC Persian.