Eleven people were killed Saturday in an aerial attack by Iranian forces on the headquarters of the Iranian opposition Kurdistan Democratic Party and a refugee camp in the Iraqi town of Koya, a KDP statement said.
The KDP statement added General Secretary Mustafa Maoulodi and predecessor Khalid Azizi were among the more than 30 others who were injured.
The director of the city's hospital, Kamran Abbas, confirmed the attack and causalities, the French news agency reported.
Iran did not acknowledge the attack, which reportedly occurred as the leftist group was holding a meeting. Iran considers the KDP to be a terrorist group.
The attack occurred after the KDP carried out attacks inside Iran from its bases in northern Iraq, which marked the end of a 20-year cease-fire between its fighters and Iran.
Several KDP leaders have been assassinated by Tehran in the past. Iran has also carried out repeated attacks against KDP bases along the border it shares with Iraq.
The KDP is the oldest Kurdish movement in Iran, where Kurds represent about 10 percent of the country's population of 80 million people.