A reformist website also published the names of 72 people it said had been killed in unrest following the disputed June presidential election.
Some 30 died from gunshot wounds, others from baton blows, one had his throat slit, one was thrown from the third floor of a building and one woman was burnt beyond recognition, it said.
The cancellation of next week's ceremony may reflect authorities' concern it could have become the scene of renewed opposition protests against hardline President Mahmoud Ahmadinejad and his re-election.
The poll results sparked huge opposition demonstrations, plunged Iran into its deepest internal crisis since the 1979 Islamic Revolution and further strained ties with the West.
The Mardomsalari newspaper cited "pressure" on the family of late revolutionary leader Ayatollah Ruhollah Khomeini to call off the speeches traditionally held at his shrine near Tehran to mark the seventh century death of Imam Ali, Shi'ite Islam's most revered figure after the Prophet Mohammad.
"This is the first year in which the mourning is not held at the Imam's (Khomeini's) shrine," Mardomsalari said. "The official communique says the Imam's shrine is unable to hold the mourning period in view of the problems it is facing."
MOURNING
The newspaper gave no further explanation for the unprecedented move to cancel the mourning ceremony which was to have been held over three nights between Sept 9-11.
Reformist former President Mohammad Khatami normally speaks on one of the nights at Khomeini's shrine. Several of Khatami's close allies have been detained since the June presidential poll, which moderates say was rigged in favour of Ahmadinejad.
Other newspapers also carried similar reports, which did not say whether Khatami might appear at any of the many other such events held at the same time in mainly Shi'ite Iran.
Mardomsalari said Hassan Khomeini, grandson of the Islamic Republic's founder and in charge of the shrine, was "ideologically closer" to Khatami and Mousavi and that there were indications of differences of opinion with the government.
Authorities put the death toll in post-election violence at 26 and say the dead include members of the pro-government Islamic Basij militia which was used to put down the protests.
But the reformist Norooz website said 72 "martyrs" had been killed in the protests and none of the people it listed were members of state security forces.
The list included eight women, students and others. The Norooz website, which did not give a source, also gave information on when and where many of them were killed.
One person listed by Norooz, chemistry student Kianush Asa, died "as a result of gunshot wounds" in Tehran's Freedom Square on June 15. Another, Alireza Eftekhari, 29, died on the same day and place "as a consequence of baton blows to the head." (Additional reporting by Hashem Kalantari; Editing by Jon Hemming)
