This is being seen as a crucial day in Iran after yesterday's threatening speech by Ayatollah Ali Khamenei. Will the opposition movement defy the supreme leader and take to the streets again to protest about the disputed re-election of Mahmoud Ahmadinejad? And if there is another big rally how will the security forces react? Follow live updates

Supporters of defeated reformist presidential candidate Mir Hossein Mousavi demonstrate in Tehran, Iran. Photograph: Getty Images/Getty Images

2.25pm:
One person has been killed in an explosion near the shrine of Ayatollah Ruhollah Khomeini, in Tehran, according to the Fars News Agency.

Two people were injured, Reuters quotes it saying.

2.20pm:
There are heavy clashes on Azadi Street, and chants of death to Khamenei, according to this regularly updated live blog from Iran. It also reports intense clashes on Enghelab Square. It's impossible to verify this at the moment.