By Jim Muir
BBC correspondent in Tehran
Hundreds of protesters in the Iranian capital, Tehran, have been signing up to carry out suicide attacks against coalition forces in Iraq.
Heavy policing has protected the UK embassy from protesters
The symbolic signing took place on what has been billed as a day of mourning over the apparent desecration of holy Shia sites by foreign soldiers in Iraq.
A demonstration has also been held outside the British embassy in Tehran - the sixth in less than two weeks.
The embassy is bearing the brunt of Iranian anger at coalition actions.
In Palestine Square, close to where Friday prayers are held at Tehran University, hundreds of Iranians jostled to fill in forms applying as volunteers for what are being called martyrdom operations against coalition forces in Iraq.
Mohammed Khalili, a teacher who was amongst those signing up, said: "My duty today is just teaching, but if it is the duty to be killed in the way of Islam, I am ready."
Most of those signing up were men of all ages, though there were also a number of women and some young teenage boys.
For the time being though, it is just a matter of registration.
The mobilisation may have the sympathy of the authorities here, but it is not being officially encouraged.
The border is closed and, at the moment at least, there is no prospect of a flood of suicide volunteers pouring from here into Iraq.
Rajay Fahr, one of the main organisers, said martyrdom operations were not seen as realistically possible yet.
"Right now it is not practical, but maybe in the future," she said. "Everything depends on the future - what happens in Iraq and what will be the situation."
At the nearby British embassy, meanwhile, there was yet another angry protest demonstration at American and British actions in Iraq - especially the hostilities around the Shia holy shrines at Najaf and Karbala.
A core of about 100 protesters pelted the main embassy building with stones, breaking more windows, and a number of percussion devices were also thrown.
But the demonstrators were heavily outnumbered by well-prepared and equipped riot forces.
The authorities are clearly determined to prevent any serious attack on the embassy compound.