Iranian shelling has killed the deputy military leader of The Party of Free Life of Kurdistan (PJAK), a north Iraq-based Kurdish separatist group, it said in an online statement.
"Majid Kawian, known as Comrade Samkou, deputy commander general of the forces of eastern Kurdistan in the Party of Free Life of Kurdistan, was killed ... in heavy Iranian shelling" on Saturday, said the statement posted on PJAK's website late on Tuesday.
Kawian was born in 1982 in Iran and has been a member of PJAK since 1999, the statement said.
The Iranian Revolutionary Guards had earlier said on their website Sapahnews that Kawian had been killed, citing the PJAK statement.
Kawian had been engaged in "terrorist operations inside Iran" since 2003, according to the Guards.
In July, Iran launched a major offensive against PJAK rebels, shelling districts near Iraq's border for weeks, but halted it during the Muslim holy month of Ramadan to give the rebels a chance to withdraw from border areas.
The Guards resumed the offensive on Friday, with their operations officer Colonel Hamid Ahmadi saying the fighting would "continue until all counter-revolutionaries, rebels and terrorists have been cleared away."
According to the Guards, more than 30 PJAK rebels have been killed and 40 wounded in the second wave of attacks, while Iran has suffered two casualties.
On Monday, PJAK declared a truce and called on Iran to reciprocate in order to prevent further bloodshed.
Iran responded a day later, saying Iraq's Kurdish autonomous government, which is acting as a mediator, must clarify the details of the truce.
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"Since the content of the unilateral ceasefire announced by the PJAK terrorist group is not clear-cut, the government of the autonomous (Iraqi) Kurdistan region which mediated this act, should clarify the intention of the ceasefire as soon as possible," the Guards said.
PJAK rebels have engaged in numerous clashes with Iranian forces in recent years, and Iran has often then bombed their rear-bases in mountainous border districts of Iraqi Kurdistan.
In mid-August, Turkey began its own campaign of shelling and air raids against bases of the Kurdistan Workers' Party (PKK) in Kurdistan, which has ties with the PJAK.
Tehran has accused neighbouring Iraq's autonomous Kurdistan region of creating a safe haven for terrorists, and has rejected criticism from Baghdad that Iran should stop the border shelling.
On Tuesday, the president of Iraq's Kurdistan region, Massud Barzani, called on Kurdish fighters seek their goals through diplomacy.
"We are in a difficult situation because there are two countries (Iran and Turkey) telling us to control our borders so there will be no problems," Barzani said in Arbil.
But "we are afraid to send forces to the borders for fear of a Kurdish-Kurdish war," he said.
"I call on the two sides to stop the idea of getting their rights through military means."
Human Rights Watch meanwhile has criticised Iran over its military operation, saying it had evidence its forces may have deliberately targeted civilians.
It also accused Turkey of failing to take adequate precautions to protect civilians in its campaign of shelling and air raids against suspected bases of PKK rebels in northern Iraq.