An attack Saturday on a Democratic Party of Iranian Kurdistan base in Iraq killed at least 11 people and wounded 50, the separatist group said, with officials immediately blaming Iran for the assault.
Iranian state media and its military forces did not immediately acknowledge the attack in Koya, some 300 kilometers (185 miles) north of Baghdad.
The party, known by the acronym PDKI, on Twitter accused Iran of using "long-range missiles in a coordinated attack on PDKI's bases and adjacent refugee camps." It posted pictures of smoke rising from the attacks.
The secretary-general of the separatist group, Mustafa Mawludi, and his predecessor, Khalid Azizi, were wounded, the Kurdish satellite news channel Rudaw reported.
The attack comes after the PDKI accused Iran on Friday of carrying out "indiscriminate shelling" targeting the border region between Iran and Iraq.
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Iranian media on Saturday also reported authorities hanged three Kurd prisoners after years in prison.
Kurds represent about 10 percent of Iran's population of 80 million people, with many living in the mountainous northwest that borders Iraq and Turkey.
A breakaway Kurdish republic backed by the Soviets briefly emerged after World War II and a Kurdish uprising followed in the years after Iran's 1979 Islamic Revolution. A guerrilla campaign by PDKI fighters in Iran continued into the mid-1990s. Ultimately, the PDKI declared a unilateral cease-fire with Iran in 1996 after fighting in northern Iraq between warring Kurdish forces backed by Iraq and Iran.
Kurdish resentments have grown recently, buoyed by Kurdish control of areas in northern Iraq. In one incident, the death of a Kurdish maid at a hotel in the northwestern city of Mahabad in May 2015 sparked unrest by local Kurds as opposition groups alleged Iranian security forces somehow had a hand in it.
Since 2016, clashes have erupted between Kurdish fighters and Iranian security forces, including the elite Revolutionary Guard, leading to casualties on both sides. The PDKI, operating out of the northern Iraq, claimed many of those attacks, which saw Iranian forces shell Kurdish positions just across the Iraqi border in response.