Two suicide bombers have attacked offices of the two main Kurdish parties in northern Iraq, killing scores of people. The BBC's Barbara Plett in Baghdad looks at the issues behind the attacks in Irbil.
Q: Why attack these targets?
No-one has claimed responsibility for either of these attacks at the offices of the of the Kurdistan Democratic Party (KDP) and the Patriotic Union of Kurdistan (PUK). These groups are two of the closest and most powerful allies of the Americans and therefore, viewed as collaborators by the radical nationalists and Islamists who are believed to make up the core of the anti-occupation insurgency.
Q: Why now?
Sunday is the first day of the Muslim holiday Eid al-Adha. Some Islamic militants consider holy days an auspicious time to carry out attacks against those they consider infidels.
Operationally the Eid provided a soft but high profile target, many senior Kurdish officials were present but security was lax because this was a time for people to come and offer greetings for the festive season.
And there is increasing attention on Kurdish demands for an enlarged autonomy in a federal structure, which many Iraq Arabs oppose as a first step to independence and the break-up of the country.
Q: Who might have carried out the attacks?
Some Kurdish officials have already blamed Islamic extremists, particularly members of a local group known as Ansar al-Islam. Ansar had a stronghold in PUK territory before the US-led war that toppled Saddam Hussein. There has been a history of conflict between the PUK and Ansar.
It scattered over the Iranian frontier after being attacked by US forces and PUK Peshmerga fighters during the war, but US officials say it has regrouped and may have joined elements of the resistance.
Q: Is there a connection to al-Qaeda?
US and Iraqi officials have said that Ansar has links to al-Qaeda. Allegations last year that a purported al-Qaeda operative, Abu Musab Zarqawi, had established a "poison and explosives training centre camp" in Ansar territory formed a key part of the US administration's argument.
However the group's leader has strongly denied such links. Some analysts have said there's no hard evidence to suggest that Ansar is more than a minor irritant in local Kurdish politics, and that Kurdish officials may have played up the threat it posed for their own purposes.
Q: Willl the attacks have a political impact?
There have been a number of attacks in Irbil, but generally the north has been relatively quiet. Sunday's suicide bombings show the ability of insurgents to strike devastating blows at will and create an atmosphere of instability, which presumably is their goal.
This may also increase ethnic tensions, because it will probably harden Kurdish demands for autonomy, including semi-sovereign control of military forces. And this could complicate both Iraqi and American efforts to persuade the Kurds to downplay or defer their controversial demands until after Iraqi general elections at the end of 2005.