Rockets have struck the headquarters of two Iranian Kurdish opposition parties in Iraq's semi-autonomous Kurdish region, with reports saying at least 11 people have been killed and 50 others wounded.
The missiles hit the headquarters of the Kurdistan Democratic Party of Iran (KDPI) and the Democratic Party of Iranian Kurdistan (PDKI) on Saturday in the town of Koya, 300km north of Iraq's capital, Baghdad.
In a post on Twitter, the PDKI blamed Iran for the attack and said that an adjacent refugee camp was also hit.
Photos posted by PDKI on social media showed injured children and massive plumes of smoke in the sky.
Al Jazeera could not verify the report independently. Iranian state media and its military have not commented on the reported attack.
The two separatist groups seek Kurdish autonomy in Iran and operate in exile in neighbouring Iraq.
Kurds account for about 10 percent of Iran's population of 80 million people, with many living in the mountainous northwest region 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.
An armed campaign by PDKI fighters in Iran continued into the mid-1990s. Ultimately, the PDKI declared a unilateral ceasefire with Iran in 1996.
Deadliest since 1996
News channel Kurdistan 24 said the attack occurred at a meeting of the PDKI leaders, adding that at least two senior officials - secretary-general Mustafa Mawludi and his predecessor Khalid Azizi - were wounded in the shelling.
Saturday's attack was the deadliest on the party's headquarters since 1996, the channel said. It came a day after the PDKI accused Iran of conducting "indiscriminate shelling" at the border region between Iraq and Iran.
The PDKI also staged attacks across the border in Iran on Friday, ending a 20-year ceasefire with the Islamic Republic, according to dpa news agency.
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 Koya.
Koya, also known as Koysinjaq, is about 60km east of the autonomous Kurdish region's capital Erbil. Citing local officials, Rudaw, a Kurdish television channel, said the Koya region "has been under bombardment for days".
Meanwhile, Iran on Saturday executed three alleged Kurdish separatists, according to Iran's Fars news agency.
One of them, Ramin Hossein Panahi, had planned to bomb a rally in Iran's Kurdish province last June, Fars said. Zaniar Moradi and Loghman Moradi were executed for being members of an unnamed "terrorist separatist group" and of killing people, the report added.
On Friday, Iran's Revolutionary Guard Corps admitted to killing six members of a Kurdish armed group involved in a July attack on an Iranian border post.