Arbil - An al Qaeda affiliate claimed responsibility for a rare bomb attack in Iraq's usually peaceful Kurdistan region and said it was in revenge for the enclave's support for fellow Kurds fighting Islamists in Syria.
At least six people were killed when militants tried to storm the headquarters of the security services in the Kurdish capital Arbil last month in the first big attack there since 2007.
In recent months, a Kurdish militia has been fighting mainly Arab rebels and Islamists in northern Syria, opening an ethnic front in a civil war that has increasingly been fought along sectarian lines.
Iraqi Kurdistan's President Masoud Barzani said in August his well-armed region was ready to defend Kurds in Syria, but his chief of staff later clarified there were no plans to send troops across the border.
The Islamic State of Iraq and the Levant said in a statement it had carried out the attack in response to threats by Barzani, whom the group described as a "criminal apostate".
The Islamic State of Iraq and the Levant (Isil) was formed in April through a merger between al-Qaeda's Syrian and Iraqi affiliates.
The combined group has claimed responsibility for attacks on both sides of the border and has fought Kurds affiliated with the Democratic Union Party (PYD), which dominates in Syria and is aligned with the Kurdistan Workers' Party (PKK).
Barzani is in fact closer to a group of Syrian Kurdish parties that are opposed to the PYD, which they accuse of being in league with President Bashar Assad and seeking to replace his authoritarian one-party rule with its own.
Kurdistan has largely managed to insulate itself from the violent instability that afflicts the rest of Iraq, attracting major international companies to invest in the autonomous region.
More than 200 000 Syrian refugees, most of them Kurds, have fled to safety among their ethnic kin in Iraq since the start of the conflict more than two years ago.