A parked motorcycle and an explosive device were detonated late on Tuesday next to the headquarters of the Democratic Party of Iranian Kurdistan (PDKI) in Koy Sanjaq, east of Irbil.
The attack took place as party members celebrated the winter solstice.
It was not immediately clear who was behind the blasts.
Jihadist militants from so-called Islamic State (IS), whom Kurdish forces are battling in northern Iraq, have carried out similar attacks in Iraq`s semi-autonomous Kurdistan Region.
But the PDKI, which has been striving for decades for autonomy for predominantly Kurdish areas in north-western Iran, has also been involved in armed clashes with Iran`s Revolutionary Guards.
Fighting near the Iraqi border in June and July left several dead on both sides.
Iraq bomb attack targets Iranian Kurdish opposition party
21 December 2016
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Seven people have been killed and 15 wounded in a bomb attack on the offices of an Iranian Kurdish opposition party in northern Iraq, security sources say.
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