11 people were killed and 50 others were injured in an attack on a camp of the Democratic Party of Iranian Kurdistan in northern Iraq, according to local media, with officials immediately blaming Iran for the assault.
The Democratic Party of Iranian Kurdistan is blacklisted as a "terrorist" group by Tehran.
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.
"11 people were killed and 50 refugees were wounded in the attack," the PDKI said on Twitter. The strike targeted a conference held by the political office of the party this morning.
A PDKI leader, Mohammed Saleh Qadri, told dpa that Iranian drones took off from the oil-rich city of Kirkuk and hit the party's bases in the Kurdish town of Koya in Irbil province, the capital of the Kurdistan region.
Major General Jabbar Yawar, a spokesman for Iraq's Kurdish Peshmerga security forces, said the area that had been attacked included a residential complex for the families of party members.
If confirmed, it would be the deepest recent strike by Tehran into Iraqi Kurdistan.
The Iranian Foreign Ministry could not be reached for comment, and there were no reports of the incident on the main Iranian news agencies.
The Kurdistan Regional Government (KRG) condemned the shelling on Saturday, saying regional laws and territorial integrity should be respected.
The attack comes after the PDKI accused Iran on Friday of carrying out "indiscriminate shelling" targeting the border region between Iran and Iraq.
Iranian media on Saturday also reported authorities hanged three Kurd prisoners after years in prison.
Iran has in the past shelled armed rebel groups based in Iraq.