"The terrorists' headquarters... was successfully struck by seven surface-to-surface rockets on Saturday by the missile department of the Guards' aerospace force," it said on its Sepah News website.

The statement added that their drone division was also involved.

Fifteen people were killed in the rare cross-border attack on the Kurdistan Democratic Party of Iran, which is blacklisted as a "terrorist" group by Tehran, a KDPI spokesman, Soran Louri, told AFP on Sunday.

Around 30 others were injured, according to local medical sources.

Iranian state television showed images of the missiles being launched and drone footage of the impact.

"The punishment of transgressors was planned following the recent months' wicked acts by terrorists from the Kurdistan realm against the Islamic republic's borders," the Guards' statement said.

It cited incursions by numerous "terrorist teams" into Iran's West Azarbaijan, Kurdistan and Kermanshah provinces bordering Iraq.

The KDPI had recently clashed with Revolutionary Guards forces in the towns of Marivan and Kamyaran in Iran's own Kurdistan region, the statement added.

The Kurdish group was holding a meeting at the time of the missile strikes, and the party's secretary general and his predecessor were injured, according to one of its officials.

The headquarters is in Koysinjaq, around 60 kilometres (35 miles) east of Arbil, capital of Iraq's autonomous Kurdish region.

Iraq's foreign ministry denounced the Iranian missile strike.

"Iraq protects the security of its neighbours and does not allow its territory to be used to threaten these countries," spokesman Ahmed Mahjoub said in a statement.

"But it categorically rejects the violation of its territorial sovereignty by strikes against certain targets on its territory with previous coordination," he added.

The KDPI is Iran's oldest Kurdish movement and has seen several of its leaders assassinated by Tehran in the past.