"On Thursday, security forces arrested Faik Mohammed Kolbi, the leader of the Kurdish Democratic Solution," an Iraqi officer said in Sulaimaniyah, a majority Kurdish Iraqi city 300 kilometres (185 miles) north of Baghdad.

The KDS is an Iraqi ally of the outlawed Kurdistan Workers' Party (PKK), which has been fighting the Turkish army in Kurdish majority areas of southeastern Turkey since 1984 in a war which has claimed 37,000 lives.

Last month, Iraqi Prime Minister Nuri al-Maliki promised Ankara that the PKK would no longer be allowed to operate in Iraq after allegations that it had mounted renewed cross-border raids.

Kolbi was arrested as a suspect in the February 2005 murder of a PKK dissident, Kamal Shahin, the Iraqi security official said.

Supporters dismissed the explanation and argued that Kolbi's detention was a sop to Turkey from Iraqi authorities eager to show that they are serious in their crackdown.

Kolbi is a former surgeon who has been a leading Kurdish militant since 1980 and was elected to the parliament of Iraq's autonomous Kurdish region in 1992. He has led the KDS since 2001.