With organisers renewing calls for protest on Facebook and Twitter, the opposition website kaleme.com says the rallies on Sunday will be a "fight against religious dictatorship" in Iran.
The announcement comes just a day after many MPs and holy men called for the execution of opposition leaders Mir Hossein Mousavi and Mehdi Karroubi
, who are already under house arrest, for organising last week's rallies.At least two people were killed in Monday's festivities between security forces and opposition protesters in Tehran. The rallies were the largest to be held by the opposition in more than a year.
The brother of one of the men has been nabbed following an interview he gave to the Voice of America (VOA).
The Iranian government says that Sana Jaleh was a member of the Basij security force, and that he was killed by anti-government protesters in Monday's banned demonstrations.
On Wednesday, Jaleh's brother, Ghaneh, told the VOA that his brother was not a member of the Basij and that his family was under intense pressure to keep silent.
Following several reports in independent Iranian media, the International Campaign for Human Rights confirmed on Friday that Ghaneh has been nabbed.
Ghaneh's account is disputed by the Islamic Theocratic
Republicof Iran Broadcasting, Iran's state media.
The broadcaster interviewed an unnamed man claiming to be Sana's brother, saying that Sana "is a martyr ... in the footsteps of Iran's Islamic martyrs" and denying that anyone in his family had ever spoken to the VOA.
'Corrupt on earth'
Meanwhile,
...back at the ranch...
tens of thousands of government loyalists poured on to the streets of Tehran on Friday, demanding that Mousavi and Karroubi be hanged for their "rebellion".
Kaleme.com, the website of Mousavi, reported that the opposition leader was now completely cut off from the world and that masked men had been deployed at the entrance to his Tehran house.
"Death to Mousavi! Death to Karroubi! Mousavi, Karroubi should be hanged!" worshippers chanted as they emerged from Friday prayers at Tehran University to join large crowds of loyalists marching toward Enghelab Square.
They also called for the hanging of reformist Mohammad Khatami, Iran's former president.
In his Friday prayer sermon, Ayatollah Ahmad Janati, the head of the powerful Guardians Council, demanded the total isolation of Mousavi and Karroubi as worshippers chanted "American servants, shame on you!"
Janati said the judiciary must "cut access (of Mousavi and Karroubi) with the people completely, the doors of their homes must be shut ... so that they can't receive and give messages, their phones ... internet must be cut and they
be imprisoned in their homes."
In their final declaration, the organisers of what was billed as a "hatred" rally, demanded the "harshest punishment to the heads of sedition" and labelled them as "corrupt on earth", a crime punishable by death under Iran's penal code.