By Jim Muir
BBC correspondent in Tehran
The bomb attacks on Karbala and Baghdad dominate Wednesday's front pages in Tehran.
Many Iranians were among those killed and injured in the attacks
There were tens of thousands of Iranian pilgrims at the Shia holy places in Iraq for Ashura, and many of them were among the casualties.
One newspaper, Sharq, reports that about 40 Iranians were killed, and many others were injured in the blasts.
Ashura commemorates the killing of the revered Imam Hussein at the battle of Karbala in the seventh century AD.
It is the event that gave birth to the Shia branch of Islam which predominates in Iran.
So Ashura is by far the most significant day in the Iranian religious calendar, and it is commemorated as a slaughter of innocents by traitors and tyrants.
'Day of martyrdom'
Not surprisingly, several of today's papers carry headlines such as "Another Ashura in Karbala", and there are many references to the shedding of blood on this day of martyrdom.
But one of the hard-line dailies, Jomhuri-ye-Eslami, breaks the mould by stating boldly: "America spills the blood of Shia mourners in Iraq".
That reflects the reflex reaction of Iranian officials, who were quick to hold the American-led coalition responsible for the attacks, because it is supposed to be in charge of security in Iraq.
But one of the more liberal papers, Aftab-e Yazd, takes issue with that line.
It says it is all too easy to blame the Americans - but precisely because they are responsible for security, any such events which destabilise the country are not in Washington's interest, and add to its problems in Iraq, it argues.
The paper goes through the list of potential suspects, and ends up, not surprisingly, pointing the finger at al-Qaeda, which it calls a gang of Islamic criminals.
It says al-Qaeda is like a time-bomb planted in the body of the Islamic world, whose actions make the enemies of Islam rejoice.
We have to be more vigilant with regard to this anti-Islamic and anti-Iranian group, the paper warns.
Sharq compares Tuesday's attacks in Iraq with those in Pakistan and says they were different.
It points out that sectarian strife between Sunni and Shia Muslims is long-running in Pakistan, but not so in Iraq.
It says that what happened was directed from outside the country, with the most obvious suspect being al-Qaeda, which had found in Iraq's current situation an ideal place for pursuing what it called its "irrational struggle".
Iran's currently preparing to celebrate its own new year, a time of rebirth and hope.
The death and injury of so many Iranians among the victims in Karbala and Baghdad was the third tragedy for Iran in just a few weeks, following the earthquake in Bam and the explosion of a freight train which killed 300 people.
People here are hoping that the New Year will bring happier times.