The three are suspected members of the outlawed Kurdistan Workers Party (PKK), blacklisted as a terrorist group by Turkey and much of the international community, the local police source said.

The source said the suspects took part in the deadly attack at a bus stop in the busy town centre of Diyarbakir, in a restive majority Kurdish region of southeastern Turkey, in September 2006.

The PKK denied responsibility and condemned the attack, which was claimed by a little-known hardline group calling itself the Turkish Vengeance Brigade. The group said on a website that it sought vengeance for victims of the PKK.

But authorities cast doubt on this claim and the police source on Monday said the suspects had received training in bomb handling in PKK camps.

The PKK took up arms for Kurdish self-rule in 1984, triggering a conflict with the Turkish state that has left 44,000 dead, displaced thousands and led to allegations of gross human rights violations by both sides.