Walking free in the Kurdish city of Sulaimaniyah, Faik Mohammed Kolbi insisted on his innocence and showed a document from a judge ordering his release, as he was greeted by a crowd of supporters.

The arrest of Kolbi, who leads the Kurdish Democratic Solution (KDS), came a month after Iraq promised Turkey it would crack down on the Turkish Kurdish separatist rebels.

The KDS is an Iraqi ally of the 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 Kurdish northern 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, an Iraqi security official said.

Supporters ruled out any link, 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, a former surgeon who has been a leading Kurdish militant since 1980, was elected to the parliament of Iraq's autonomous Kurdish region in 1992. He has led the KDS since 2001.