They’ve been shouting “Allah Akbar” from the rooftops since 10 o’clock last night.
They say they’ll whistle throughout President Ahmadinejad’s speech later this morning.
It’s the 31st anniversary of the Islamic revolution, and Iran’s Green Movement protestors are gearing up for action.
But the government has been preparing too.
One of Iran’s most reliable bloggers, Saeed Valadbaygi, lists 15 activists and journalists arrested over the weekend.
Reporters Without Borders says at least 65 journalists are now in custody, while the International Campaign for Human Rights estimates that some 1,000 people have been imprisoned in the last two months.
The president is meant to deliver his speech to the nation from Azadi Square in the centre of Tehran.
According to the open source intelligence service Stratfor, his people will be bussed in from the south and east, while the routes from the north and west will be blocked, to stop protestors.
Last year, I was there to report the 30th anniversary of the revolution, but this time, Channel 4 News, like nearly all western media outfits, is barred.
Those journalists who’ve been allowed in may not cover the traditional march through the streets but only the speech and rally in the square, presumably to stop them seeing protestors.
There’ll be the online battle too.
The government has announced that a cable connecting the internet to the rest of the world has unfortunately been cut, and can’t be restored this week – a not very subtle way of trying to stop people sending out pictures. Chances are that mobile phone connections will be cut too.
So Twitter is buzzing with information about proxy servers and passwords, as the protestors do their utmost to get out the images and stories international journalists cannot get any other way.
On the last big protest day, 27 December, the Shi’a holy festival of Ashura, at least eight people were killed.
Such is the diffuse, decentralised nature of the opposition, it’s hard for the Iranian government to crush it, but the fear today must surely be that a high turnout of opposition supporters will be met with greater and more desperate violence.